#include <cstdio>
#include <cmath>

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define inc( i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define dec( i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

typedef long long   signed int LL;
typedef long long unsigned int LU;

template<typename T> void swap(T &x, T &y) { T t = x; x = y; y = t; return; }
template<typename T> T abs(T x) { return (0 <= x ? x : -x); }
template<typename T> T max(T a, T b) { return (b <= a ? a : b); }
template<typename T> T min(T a, T b) { return (a <= b ? a : b); }
template<typename T> bool setmin(T &a, T b) { if(a <= b) { return false; } else { a = b; return true; } }
template<typename T> bool setmax(T &a, T b) { if(b <= a) { return false; } else { a = b; return true; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

char s[2][6];
bool ans = true;

int main() {
	scanf("%s%s", s[0], s[1]);
	
	int len0 = 0, len1 = 0;
	while(s[0][len0] != '\0') { len0++; }
	while(s[1][len1] != '\0') { len1++; }
	
	if(len0 > 5) { ans = false; }
	if(len1 > 5) { ans = false; }
	
	inc(i, len0) { if('0' <= s[0][i] && s[0][i] <= '9') { } else { ans = false; } }
	inc(i, len1) { if('0' <= s[1][i] && s[1][i] <= '9') { } else { ans = false; } }
	
	if(len0 != 1 && s[0][0] == '0') { ans = false; }
	if(len1 != 1 && s[1][0] == '0') { ans = false; }
	
	if(len0 != 5 || (s[0][0] <= '1' && s[0][1] <= '2' && s[0][2] <= '3' && s[0][3] <= '4' && s[0][4] <= '5') ) { } else { ans = false; }
	if(len1 != 5 || (s[1][0] <= '1' && s[1][1] <= '2' && s[1][2] <= '3' && s[1][3] <= '4' && s[1][4] <= '5') ) { } else { ans = false; }
	
	printf("%s\n", ans ? "OK" : "NG");
	
	return 0;
}