#include <bits/stdc++.h>
using namespace std;
int main(){
  int C, Y;
  cin >> C >> Y;
  Y /= 100;
  if (Y < C){
    cout << "can't exchange" << endl;
  } else if (Y % 5 >= C){
    cout << "no exchange" << endl;
  } else {
    while (C % 5 != Y % 5){
      C++;
    }
    cout << C << endl;
  }
}