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

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	int c, y;
	cin >> c >> y;
	if(y / 100 < c) {
		cout << "can't exchange" << endl;
		return 0;
	}
	vector<int> v{10000, 5000, 2000, 1000, 500, 100}, num(6);
	rep(i, 6) {
		num[i] = y / v[i];
		y -= num[i] * v[i];
	}
	if(num[5] >= c) {
		cout << "no exchange" << endl;
		return 0;
	}
	int cc = c;
	cc -= num[5];
	int m = cc % 5;
	if(m) c += 5 - m;
	cout << c  << endl;
}