b.c

// Compile with:
// gcc -O3 -march=native -ffast-math -funroll-loops b.c
#include "stdio.h"

long sumit(long n)
{
    long i = 0, s = 0;
    while (i < n) {
        s += i;
        i++;
    }
    return s;
}

typedef long (*fn_ptr)(long);

long apply(fn_ptr f, long a)
{
    return f(a);
}

int main(int argc, char *argv[])
{
    long i = 0, sum = 0;
    if (argc != 3) return 1;
    long a, b;
    a = atoi(argv[1]);
    b = atoi(argv[2]);


    fn_ptr s = sumit;

    while (i < a) {
        sum += apply(s, b);
        i++;
    }

    printf("%ld\n", sum);

    return 0;
}