C,Y=map(int,input().split())
Y//=100
a=[Y%10//5,Y%50//10,Y%100//50,Y//100]
b=[5,10,50,100]
c=d=Y%5
for i in range(4):
	if d<C:
		if d+a[i]*b[i]>C:d+=(C-d+b[i]-1)//b[i]
		else:d+=a[i]*b[i]
print("can't exchange"if Y<C else d if c<C else"no exchange")