#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main()
{
	char s1[6];
	char s2[6];
	scanf("%s\n%s",s1,s2);
	int l1,l2;
	l1 = strlen(s1);
	l2 = strlen(s2);
	for (int i = 0;i < l1;i++) {
		if (!isdigit(s1[i]) || (s1[0] == '0' && l1 != 1)) {
			puts("NG");
			return 0;
		}
	}
	for (int i = 0;i < l2;i++) {
		if (!isdigit(s2[i]) || (s2[0] == '0' && l2 != 1)) {
			puts("NG");
			return 0;
		}
	}
	puts("OK");
}