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

int C, Y;
int m[] = {1, 5, 10, 20, 50, 100};
int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> C >> Y;
    Y /= 100;
    if(Y < C){
        cout << "can't exchange\n";
        return 0;
    }
    if(Y % 5 >= C){
        cout << "no exchange\n";
        return 0;
    }
    C -= Y % 5;
    cout << ((C + 4) / 5 * 5 + Y % 5) << "\n";
    return 0;
}