#include<iostream>
#include<string>
using namespace std;

int main(){
	char a, b;
	cin >> a;
	cin >> b;
	if(a >=0 && a <= 12345 && 0 <= b && b <= 12345 && isdigit(static_cast<unsigned char>(b)) && isdigit(static_cast<unsigned char>(a))){
		cout << a+b << endl;
	}else{
		cout << "NG" << endl;
	}
	return 0;

}