#include <iostream>

using namespace std;

int a, b;

int rev(int x)
{
	int y = 0;
	for (; x; x /= 10) y = y * 10 + x % 10;	
	return y;
}

int main()
{
	while (cin >> a >> b)
		if (rev(a) + rev(b) == rev(a + b)) cout << a + b << endl;
		else puts("NO");
	return 0;
}