//#include<iostream>
//#include<cstdio>
#include <stdio.h>
//using namespace std;
int reverse(int x){
//求反序数
int revx=0;
while(x!=0){
revx *= 10;
revx += x%10;
x /= 10;
}
return revx;
}
int main(){
int a,b,c;int a1,b1,c1;
while(scanf("%d%d",&a,&b)!=EOF){
c=a+b;
a1=reverse(a);
b1=reverse(b);
c1=reverse(c);
if(a1+b1==c1)printf("%d\n",c);
else printf("NO");
}
}

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