/*
ZADANIE 2
--------------------------------------------------------------------------------
O(1)

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
    int x, s;
    cin >> x;
    s = ((1+x)/2)*x;
    cout<<s<<endl;
    return 0;
}
--------------------------------------------------------------------------------
O(n)

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
    int x,suma = 0;
    cin>>x;
    for (int i=1; i<=x; i++)
    {
        suma+=i;
    }
    cout<<suma<<endl;
}
--------------------------------------------------------------------------------
O(n^2)

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
    int x, suma=0;
    cin>>x;
    for(int i = 1; i<=x; i++)
    {
        for(int j=1;j<=i;j++)
        {
            suma+=1;
        }
    }
    cout<<suma<<endl;
}
--------------------------------------------------------------------------------
ZADANIE 3

a) zlozonosc O(n) - iteracyjnie

#include <stdio.h>
#include <iostream>
using namespace std;
int main()
{
    int f0=0, f1=1, fn=0,n;
    cin>>n;
    for (int i=1;i<n;i++)
    {
        fn = f1 + f0;
        f0=f1;
        f1 = fn;
    }
    cout<<fn<<endl;
}

b)
*/