#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

MOD = 998244353
#############################################################

C,Y = lmin()
Y = Y//100
if Y < C:
    print("can't exchange")
elif Y%5 >= C:
    print("no exchange")
else:
    D = C-Y%5
    print(Y%5+(D+4)//5*5)