#include <bits/stdc++.h> using namespace std; int main() { int C, Y; cin >> C >> Y; if(Y % 500 >= C * 100) { cout << "no exchange" << endl; return 0; } if(Y / 100 < C) { cout << "can't exchange" << endl; return 0; } int ans = Y % 500 / 100; while(ans < C) { ans += 5; } cout << ans << endl; return 0; }