package main

import . "fmt"

func main() {
	var c,y int
	Scan(&c,&y)
	y/=100
	h:=y%10-y%10/5*5
	if h>=c {
		Println("no exchange")
		return
	}
	cc:=c-h
	yy:=y-h
	r:=(5-(cc%10-cc%10/5*5))%5
	if yy<cc+r {
		Println("can't exchange")
		return
	}
	Println(c+r)
}