PI.c

#include <stdio.h>

int main() {

    double long k = 1,
        s = 0;

    for (size_t i = 0; i < 1000000; i++)
    {
        if (i % 2 == 0)
            s += 4/k;
        else
            s -= 4/k;
        
        k += 2;
    }
    

    printf("[PI] %Lf\n", s);

    return 0;
}