C, Y = map(int, input().split())
kinds = [1, 5, 10, 50, 100, 500, 1000, 2000, 5000, 10000]
num = [0] * 10
ind = 9
while ind >= 0:
    num[ind] = Y // kinds[ind]
    Y = Y % kinds[ind]
    ind -= 1
if num[4] >= C:
    print('no exchange')
    exit()
k = 0
for i in range(4, 10):
    k += num[i] * kinds[i] // 100
if k < C:
    print("can't exchange")
    exit()

# あと最低C-num[4]枚欲しい...
print(num[4] + (C-num[4]+4)//5 * 5)