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

if y < 100 * c:
    print("can't exchange")
    exit()
C = dict()
L = [10000, 5000, 2000, 1000, 500, 100, 50, 10, 5, 1]
for n in L:
    r, y = divmod(y, n)
    C[n] = r
if C[100] >= c:
    print("no exchange")
    exit()
yy = 0
LL = [100, 500, 1000, 2000, 5000, 10000]
for n in LL:
    yy += n * C[n]
if yy < 100 * c:
    print("can't exchange")
else:
    ans = c
    yy -= c * 100
    while yy % 500 != 0:
        ans += 1
        yy -= 100
    print(ans)