#include<iostream> #include<iomanip> using namespace std; int fan(int x){ int s=0; int t=x; while(t){ s=s*10+t%10; t/=10; } return s; } int main() { int n,a,b; cin>>n; for(int i=1;i<=n;i++){ cin>>a>>b; if(fan(a)+fan(b)==fan(a+b)){ cout<<a+b<<endl; } else{ cout<<"NO"<<endl; } } return 0; }