#include <stdio.h>

long loop(long a, long b) {
    long result = 1;
    while (a < b) {
        result = result * (a + b);
        a = a + 1;
    }
    return result;
}

int main() {
    long a = 2;
    long b = 6;
    printf("loop(%ld, %ld) = %ld\n", a, b, loop(a, b));

    return 0;
}