#include <string>
#include <iostream>
using namespace std;
string Reverse(int n) {//将数字传入反转成字符串返回
string str = to_string(n);
string str1;
for (int i = str.size() - 1, j = 0; i >= 0 ; --i) {
str1[j++] = str[i];
}
return str1;
}
int main() {
int a, b;
while (cin >> a >> b) {
//字符串转换成int型
int ra = stoi(Reverse(a));
int rb = stoi(Reverse(b));
int rab = stoi(Reverse(a + b));
if (ra + rb == rab) {
cout << a + b << endl;
} else {
cout << "NO" << endl;
}
}
}

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