#include <stdio.h>

int main(void){
	int m,n,k;

	printf("1つ目の数\n");
	scanf("%d", &m);

	printf("2つ目の数\n");
	scanf("%d", &n);
	
	if(n == 0) printf("\n最大公約数は%d\n", m);
	else{
		while(n != 0){
			k = m % n;
			m = n;
			n = k;
		}

		printf("\n最大公約数は%d\n", m);
	}
		
	return 0;
}

これでいい？(;´Д`)