string 9/3

//#1
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = Console.ReadLine();
            int k = st.Length - 2;
            Console.WriteLine(st.Substring(0, 1));
            Console.WriteLine(st.Substring(st.Length - 1));
            Console.WriteLine(st.Substring(st.Length / 2, 1));
            Console.WriteLine(st.Substring(0, st.Length / 2));
            Console.WriteLine(st.Substring(st.Length/2));
            Console.WriteLine(st.Substring(0, 3));
            Console.WriteLine(st.Substring(st.Length - 3));
            Console.WriteLine(st.Substring(0, k));
            Console.WriteLine(st.Substring(st.Length - k));
            st.Replace("go", "went");
        }
    }
}

//#2
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string ktovet = Console.ReadLine();
            string city = Console.ReadLine();
            int index = ktovet.IndexOf(city);
            if (index >= 0)
               ktovet = ktovet.Remove(index, city.Length);
            Console.WriteLine(ktovet);
        }
    }
}

//#3
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "aal aiv isn't kam";
            int i = 2, counter = 0;
            if (st[0] == 'a')
                counter++;
            while (i < st.Length)
            {
                if (st[i] == 'a' && st[i-1] == ' ')
                    counter++;
                i++;
            }
            Console.WriteLine(counter);
        }
    }
}

//#4
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "aaa aia isn'a kaa";
            int i = 2, counter = 0;
            if (st[st.Length - 1] == 'a')
                counter++;
            while (i < st.Length - 2)
            {
                if (st[i] == 'a' && st[i+1] == ' ')
                    counter++;
                i++;
            }
            Console.WriteLine(counter);
        }
    }
}


//#5
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "aaY aia isn'Y kaa";
            int i = 2, counter = 0;
            if (st[st.Length - 1] == 'Y')
                counter++;
            while (i < st.Length - 2)
            {
                if (st[i] == 'Y' && st[i+1] == ' ')
                    counter++;
                i++;
            }
            Console.WriteLine(counter);
        }
    }
}

//#6
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "galnivmagniv", x = Console.ReadLine();
            int mone = 0;
            while (st.IndexOf(x) > 0)
            {
                mone++;
                st = st.Remove(st.IndexOf(x), x.Length);
            }
            Console.WriteLine(mone);
        }
    }
}

//#7
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "galnivmagniv", x = Console.ReadLine(), y = Console.ReadLine();
            int index = st.IndexOf(x);
            st = st.Insert(index, y);
            index += y.Length;
            st = st.Remove(index, x.Length);
            Console.WriteLine(st);
        }
    }
}

//#8
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] arr = { "gal", "liv", "magniv", "meod", "photography" };
            int mone = 0;
            for (int i = 0; i < arr.Length - 1; i++)
            {
                string last = arr[i], first=arr[i+1];
                last = last.Substring(last.Length - 1, 1);
                first = first.Substring(0, 1);
                if (last == first)
                    mone++;
            }
            Console.WriteLine(mone);
        }
    }
}

//#9
Go to this link the table is there - http://i.snag.gy/5S5Qu.jpg

//#10
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static void Main(string[] args)
        {
            string st = "galnivmagniv@photography.com";
            int index = st.IndexOf("@");
            if (index < 0)
                Console.WriteLine("Doesn't exist");
            else
            {
                st = st.Remove(index);
                Console.WriteLine(st);
            }
        }
    }
}

//#11
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        //א
        static string Sod0(string st)
        {
            string hafuh = "";
            for (int i = 0; i < st.Length; i++)
            {
                hafuh += st[st.Length - i - 1];
            }
            return hafuh;
        }

        //ב
        static bool Sod1(string st)
        {
            return st.Equals(Sod0(st));
        }

        static void Main(string[] args)
        {
            string st = Console.ReadLine();
            int i = 0;
            while (st != "exit")
            {
                if (!Sod1(st))
                    Console.WriteLine(Sod0(st));
                else
                    i++;
                st = Console.ReadLine();
            }
            Console.WriteLine(i);
        }
    }
}

//#12
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1524
{
    class Program
    {
        static bool Hukit(string pass)
        {
            if (pass.Length != 6)
                return false;
            int mone = 0;
            for (int i = 0; i < pass.Length; i++)
                if (Char.IsLetter(pass[i]))
                    mone++;
            if (mone < 3)
                return false;

            return true;
        }

        static void Main(string[] args)
        {
            string st = Console.ReadLine();
            if (Hukit(st))
                Console.WriteLine("WELLCOME");
            else
            {
                while (!Hukit(st))
                {
                    Console.WriteLine("ERROR, INSERT ANOTHER PASSWORD");
                    st = Console.ReadLine();
                }
                Console.WriteLine("WELLCOME");
            }
        }
    }
}

//#13
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    class Program
    {
        static string Spaces(string st)
        {
            while (st.IndexOf("  ") != -1)
            {
                st = st.Replace("  ", " ");
            }
            return st;
        }
        static void Main(string[] args)
        {
            Console.WriteLine(Spaces("a  a a a    a   a  a     a a"));
        }
    }
}