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

int main()
{
    long long c, y;
    cin >> c >> y;

    vector<int> yen(10, 0);
    int kind[] = {1, 5, 10, 50, 100, 500, 1000, 2000, 50000, 10000};

    for (int i = 9; i >= 0; i--)
    {
        yen[i] = y / kind[i];
        y %= kind[i];
    }

    long long sum = 0;
    for (int i = 0; i < yen.size(); i++)
    {
        if (kind[i] >= 100)
            sum += yen[i] * kind[i];
        else
            yen[i] = 0;
    }
    if (sum < c * 100)
    {
        cout << "can't exchange" << endl;
    }
    else if (yen[4] >= c)
    {
        cout << "no exchange" << endl;
    }
    else
    {
        long long notEnough = c - yen[4];
        cout << yen[4] + ((notEnough + 4) / 5) * 5 << endl;
    }
}