Кама - 1

#include <iostream>
#define _USE_MATH_DEFINES
#include <cmath>
using namespace std;

double Calc(double epsilon){
    double a = 1.0;
    int i = 1;
    double res = 0.0;
    while(abs(a) > epsilon){
        res+=a;
        a= - a * ( (2.0*i-1.0) / (2.0*i+1.0) );
        i++;
    }
    return res;
}
int main() {
    double epsilon,res;
    cin >> epsilon;
    res = Calc(epsilon);
    cout << res;
    cout << endl <<  M_PI / 4 ;
}