import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
input = sys.stdin.readline
c,y = map(int,input().split())
if y // 100 < c:
    exit(print('can\'t exchange'))
d = collections.defaultdict(int)
z = [1,5,10,50,100,500,1000,2000,5000,10000]
for i in reversed(z):
    d[i] = y // i
    y %= i
if d[100] >= c:
    exit(print('no exchange'))
print((c+5-1)//5)
exit()
ans = 0
now = d[100]
for i in reversed(z):
    if i <= 100:
        break
    if now >= c:
        break
    while d[i] > 0 and now < c:
        now += i // 100
        d[i] -= 1
        ans += 1
print(ans)