#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

const unsigned N = 1000000000;

double szacuj_pi()
{
    unsigned n = 0;
    double x, y;

    srand(time(nullptr));

    for(unsigned i = 0; i < N; ++i)
    {
        x = 1.0 * (rand() - 1) / (RAND_MAX - 1);
        y = 1.0 * (rand() - 1) / (RAND_MAX - 1);
        if(x * x + y * y <= 1)
            ++n;
    }

    return 4.0 * n / N;
}

int main()
{
    cout << szacuj_pi() << endl;
    return 0;
}