C,Y=map(int, input().split())
#A=list(map(int, input().split()))
D=[10000,5000,2000,1000,500,100,50,10,5,1]
E=[]
for d in D:
  c=Y//d
  E.append(c)
  Y-=d*c
#print(E) 
c=0
if E[5]>=C:
  print('no exchange')
  exit()
for i in range(len(D)):
  if D[i]>=100:
    c+=(D[i]//100)*E[i]
if c<C:
  print("can't exchange")
  exit()
c=E[5]
d=(C-c-1)//5+1
print(E[5]+5*d)