from collections import defaultdict
C,Y=list(map(int,input().split()))
coin=[1,5,10,50,100,500,1000,2000,5000,10000]
L=len(coin)

cnt=defaultdict(int)
for i in range(L-1,-1,-1):
    cnt[coin[i]]=Y//coin[i]
    Y-=cnt[coin[i]]*coin[i]

if cnt[100]>=C:
    print("no exchange")
    exit(0)

can_exchange_money=0
for (k,v) in cnt.items():
    if k>100:can_exchange_money+=k*v
if cnt[100]+can_exchange_money//100<C:
    print("can't exchange")
    exit(0)
ans=cnt[100]
while True:
    ans+=5
    if ans>=C:
        print(ans)
        exit(0)