#include <iostream>
#include <math.h>

using namespace std;

int f_1()
{
    int n, m, sum = 0;
    cin>>n>>m;
    for(int i = 5; i < n; i += 5)
    {
        if(i % m != 0)
            sum += i;
    }
    return sum;
}

int f_2()
{
    int a, pr = 1;
    cin>>a;
    if(a >= 0)
    {
        for(int i = 2; i <= 8; i += 2)
        {
            pr *= i * i;
        }
        pr -= a;
    }

    else
    {
        for(int i = 3; i <= 9; i += 3)
        {
            pr *= (i - 2);
        }
    }
    return pr;
}

int n;

long double abs_f(long double a)
{
    if(a > 0)
    {
        return a;
    }
    if(a <= 0)
    {
        return -a;
    }
}

long double s_f(long double x)
{
    long double sum = - 2 * x * x;
    n = 0;
    long double last = sum;
    while(abs_f(sum - (sum + (-2 * x * x / (n * (2 * n - 1)) * last))) > 0.0000001)
    {
        n++;
        sum += -2 * x * x / (n * (2 * n - 1)) * last;
        last = -2 * x * x / (n * (2 * n - 1)) * last;
    }
    return sum;
}

long double y_f(long double x)
{
    return cos(2 * x) - 1;
}

int f_3()
{
    cout<<"Введите точность"<<endl;
    int akk;
    cin>>akk;
    for(long double i = 0.; i <= 1; i += 0.2)
    {
        //cout.width(15);
        cout.precision(akk);
        cout<<i<<' '<<y_f(i)<<' '<<s_f(i)<<' '<<n<<endl;
    }
}

double f_4(int n, double x)
{
    if(n == 0)
        return 1;
    else
        return f_4(n - 1, x) * x * x / (2 * n * (2 * n - 1)) + f_4(n - 1, x);
}

main()
{
    system(" chcp 1251 > nul");
    cout<<"Bведите номер задачи, которую необходимо решить"<<endl;
    int a;
    cin>>a;
    if(a == 1)
    {
        char flag = 'y';
        while(flag == 'y')
        {
            cout<<f_1();
            cout<<endl<<"Продолжить работу?(y/n)"<<endl;
            cin>>flag;
        }
    }
    if(a == 2)
    {
        cout<<f_2();
    }
    if(a == 3)
    {
        f_3();
    }
    if(a == 4)
    {
        int n;
        double x;
        char flag = 'y';

        while(flag == 'y')
        {
            cin>>n>>x;
            cout<<f_4(n, x)<<endl;
            cout<<f_4(3, x)<<endl;
            cout<<f_4(5, x)<<endl;
            cout<<f_4(10, x)<<endl;
            cout<<endl<<"Продолжить работу?(y/n)"<<endl;
            cin>>flag;
        }
    }
}