C,Y=map(int,input().split())
keta=[1,5,10,50,100,500,1000,2000,5000,10000]
count=[0]*10
for i in range(9,-1,-1):
    count[i]=Y//keta[i]
    Y-=keta[i]*count[i]
if count[4]>=C:
    print('no exchange')
    exit(0)
all=count[4]
ans=0
for i in range(9,4,-1):
    for j in range(count[i]):
        all+=keta[i]//keta[4]
        if all>=C:
            print(all)
            exit(0)
print('can\'t exchange')