c, y = map(int,input().split())

a = [1, 5, 10, 50, 100, 500, 1000, 2000, 5000, 10000]
b = [0] * len(a)

for i in range(len(a)-1,-1,-1):
	t = y // a[i]
	b[i] += t
	y %= a[i]

if b[4] >= c:
	print("no exchange")
	exit()

cnt = 0
piv = len(a) - 1
g = b[4]%5
while b[4] < c:
	if piv == 4:
		print("can't exchange")
		exit()
	if b[piv] == 0:
		piv -= 1
		continue
	b[4] += a[piv] // 100
	b[piv] -= 1
	cnt += 1

print(g + ((c-g+4)//5)*5)