def solution(phone_book):
dic={}
for number in phone_book:
dic[number]=len(number)
dicItems=dic.items()
dicItemsSort=sorted(dicItems,key=lambda item : item[1])
for i in range(len(dicItemsSort)):
pick=dicItemsSort[i][0]
for j in range(i+1,len(dicItemsSort)):
if dicItemsSort[j][0].find(pick)==0:
return False
return True