一道C语言的题，望解答

供参考：

#include <stdio.h>
int MaxCommonFactor(int a, int b)
{
    int i, min;
    if (a <= 0 || b <= 0)
        return -1;
    min = a > b ? b : a;
    for (i = min; i >= 1; i--)
        if (a % i == 0 && b % i == 0)
            return i;
}
int main()
{
    int a, b;
    scanf("%d,%d", &a, &b);
    printf("%d", MaxCommonFactor(a, b));
    return 0;
}