#include <bits/stdc++.h>
using namespace std;

int main() {
  int C, Y; cin >> C >> Y;
  vector<int> val = {1, 5, 10, 50, 100, 500, 1000, 2000, 5000, 10000}, coin(10);
  if (Y / 100 < C) { cout << "can't exchange" << endl; return 0; }
  for (int i = 9; i >= 0; i--) {
    coin.at(i) = Y / val.at(i);
    Y %= val.at(i);
  }
  if (coin.at(4) >= C) { cout << "no exchange" << endl; return 0; }
  cout << coin.at(4) + (C - coin.at(4) + 4) / 5 * 5 << endl;
}