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

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);


    int C,Y; cin >> C >> Y;
    if(C*100 > Y){cout << "can't exchange" << endl; return 0;}

    int N = 10;
    vector<int> money = {1,5,10,50,100,500,1000,2000,5000,10000};
    reverse(money.begin(),money.end());
    vector<int> have(N);
    for(int i=0; i<N; i++) have.at(i) = Y/money.at(i),Y %= money.at(i);
    if(have.at(5) >= C){cout << "no exchange" << endl; return 0;}

    cout << C+(5-C%5)%5 << endl;
}