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

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

    int c,y;
    cin >> c >> y;
    vector<int> yens = {10000,5000,2000,1000,500,100};
    vector<int> count(6,0);
    int ma = 0;
    for (int i = 0; i < 6; i++){
        count[i] += y/yens[i];
        y %= yens[i];
        ma += yens[i]/100 * count[i];
    }

    if (count[5] >= c){
        cout << "no exchange" << endl;
        return 0;
    }
    if (ma < c){
        cout << "can't exchange" << endl;
        return 0;
    }

    int ans = (5 - ((c-count[5])%5))%5 + c;
    cout << ans << endl;


    return 0;
}