import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

c,y = map(int,input().split())
y //= 100

if y < c:
    print("can't exchange")
elif y%5 >= c:
    print("no exchange")
else:
    ans = y%5
    c -= ans
    left = 5*((c+4)//5)
    ans += left
    print(ans)