编辑代码

#include <stdio.h>
int gcd(int m, int n)
{
	if (m*n <= 0)
		return -1;
	int i = m < n ? m : n;
	for (; i>=1; i--)
		if (m%i==0 && n%i==0) break;
	return i;
}
int main()
{
	int M = -5;
	int N = 9;
	int O = 8;
	int P = 6;
	printf("%d\n", gcd(M, N));
	printf("%d\n", gcd(N, O));
	printf("%d\n", gcd(N, P));
	return 0;
}