#include <bits/stdc++.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define watch(a) { cout << #a << " = " << a << endl; }
template<class T1, class T2> inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); }
template<class T1, class T2> inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); }
template<class T> void operator>> (istream& ist, vector<T>& vs) { for(auto& e: vs) cin >> e; }

typedef long long ll;
int const inf = 1<<29;

void NG() {
  cout << "NG\n";
  exit(0);
}

void OK() {
  cout << "OK\n";
  exit(0);
}

int main() {

  string A, B; cin >> A >> B;
  bool sdig = 0;

  
  rep(i, A.size()) {
    if (!isdigit(A[i])) NG();
    if (!sdig && A[i] == '0') NG();
    sdig = 1;
  }
    
  rep(i, B.size()) {
    if (!isdigit(B[i])) NG();
    if (!sdig && B[i] == '0') NG();
    sdig = 1;
  }
  OK();
  return 0;
}