# -*- coding: utf-8 -*-
"""
Created on Thu Mar 06 20:03:36 2014

@author: Michael
"""

#Assume you have a method isSubstring which checks if one word is a
#substring of another. Given two strings, s1 and s2, write code to check if s2 is
#a rotation of s1 using only one call to isSubstring (e.g.,"waterbottle" is a rotation of "erbottlewat").


def isSubstring(s1, s2):
    return s1 in s2
    
def isRotation(s1, s2):
    return isSubstring(s1, s2+s2)

print isRotation("waterbottle", "erbottlewat")
