#include <bits/stdc++.h>
using namespace ::std;
vector<string> split(const char* strTop, int length, char delm);
vector<string> split(const string& str, char delm);
typedef struct point {
  int x;
  int y;
} Point;
int main() {
  vector<int> can(3);
  for (int i = 0; i < (3); ++i) {
    cin >> can[i];
  }
  sort((can).begin(), (can).end());
  if (can[2] == can[1] + can[0]) {
    cout << ("OK") << endl;
  } else {
    cout << ("NG") << endl;
  }
  return 0;
}
vector<string> split(const char* strTop, int length, char delm) {
  vector<string> result;
  vector<char> baka;
  for (int i = 0; i < length; ++i) {
    if (*(strTop + i) == delm) {
      string tmp(baka.begin(), baka.end());
      baka.clear();
      result.push_back(tmp);
    } else {
      baka.push_back(*(strTop + i));
    }
  }
  string tmp(baka.begin(), baka.end());
  result.push_back(tmp);
  return result;
}
vector<string> split(const string& str, char delm) {
  vector<string> result;
  vector<char> baka;
  for (int i = 0; i < str.length(); ++i) {
    if (str[i] == delm) {
      string tmp(baka.begin(), baka.end());
      baka.clear();
      result.push_back(tmp);
    } else {
      baka.push_back(str[i]);
    }
  }
  string tmp(baka.begin(), baka.end());
  result.push_back(tmp);
  return result;
}
