1 #include <bits/stdc++.h> 2 #define _for(i,a,b) for(int i = (a);i < (b);i ++) 3 #define pb push_back 4 using namespace std; 5 6 int main() 7 { 8 int a,b; 9 while(cin >> a >> b) 10 { 11 if(a>b) 12 cout << a-b << endl; 13 else 14 cout << "error" << endl; 15 } 16 return 0; 17 }