toosimple.c

// [src] https://benchmarksgame-team.pages.debian.net/benchmarksgame/performance/toosimple.html
#include <stdio.h>
int main() {
    double sum = 0.0, flip = -1.0;
    for (long i = 1; i <= 10000000; ++i) {
        sum += (flip *= -1.0) / (2*i - 1);
    }
    printf("%.24f\n", sum*4.0);
}