#include <stdio.h>

int Reverse(int n)
{
	int m = 0;
	while(n)
	{
		m = m*10+n%10;
		n/=10;
	}
	return m;
}

int main()
{
	int a,b;
	while(scanf("%d %d",&a,&b) != EOF)
	{
		int sum1 = a+b,sum2;
		sum2 = Reverse(a) + Reverse(b);
		if(Reverse(sum1) == sum2)
			printf("%d\n",sum1);
		else printf("NO\n");	
	}
	return 0;
}