#include<stdio.h>
#include<string.h>

int main(void){
	char s[8],t[8];
	int i,l;
	scanf("%s%s",s,t);
	l = strlen(s);
	for(i = 0;i < l;i++){
		if(s[i] < 48 || 57 < s[i]){printf("NG\n");return 0;}
	}
	if(l != 1 && s[0] == '0'){printf("NG\n");return 0;}
	if(l == 5 && s[0]*10000+s[1]*1000+s[2]*100+s[3]*10+s[4] > 545673){printf("NG\n");return 0;}
	l = strlen(t);
	for(i = 0;i < l;i++){
		if(t[i] < 48 || 57 < t[i]){printf("NG\n");return 0;}
	}
	if(l != 1 && t[0] == '0'){printf("NG\n");return 0;}
	if(l == 5 && t[0]*10000+t[1]*1000+t[2]*100+t[3]*10+t[4] > 545673){printf("NG\n");return 0;}
	printf("OK\n");
	return 0;
}