unsigned nChoosek( unsigned n, unsigned k )
{
    if (k > n) return 0;
    if (k * 2 > n) /*return*/ k = n-k;  //remove the commented section
    if (k == 0) return 1;

    int result = n;
    for( int i = 2; i <= k; ++i ) {
        result *= (n-i+1);
        result /= i;
    }
    return result;
}

#include <stdio.h>

int main(void)
{
    printf("600 choose 3 is: %d\n", nChoosek(600, 3));
    return 0;
}