#include <iostream>
#include <vector>
#include <math.h>
using namespace std ;

int main(){
    double pi=0;
    int i=0;
    int size = 10000;
    vector<double> db(size);
        for(i=1;i<size;++i){
            double a=(2*i-1);
            if(i%2==0)
            {a=-a;}
            a=1/a;
            pi=pi+a;
            db[i] = pi;
            cout << db[i]*4 << endl;
        }
        pi=pi*4;
        cout<<pi<<endl;
        return 0;
}