import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
coin = [1, 5, 10, 50, 100, 500, 1000, 5000, 10000]
def convert_japanese_yen(yen):
    count = [0] * 9
    for i in range(8, -1, -1):
        count[i] = yen // coin[i]
        yen %= coin[i]
    return count


c, y = na()

a = convert_japanese_yen(y)

if y//100 < c:
    print("can't exchange")
elif a[4] >= c:
    print("no exchange")
else:
    print((a[4] - c)%5 + c)