Program to check anagram strings with O(n)

####################### Start of the Program

#!/usr/bin/python

first_str=raw_input("Please input first string: ")
second_str=raw_input("Please input second string: ")

def validate_anagram():
    c1=[0]*26
    c2=[0]*26
    len_iter1=len(first_str)
    len_iter2=len(second_str)
    while len_iter1>0:
        char_of_str=first_str[len_iter1 - 1]
        pos=ord(char_of_str) - ord('a')
        c1[pos]=c1[pos] + 1
        len_iter1=len_iter1 - 1
    while len_iter2>0:
        char_of_str=second_str[len_iter2 - 1]
        pos=ord(char_of_str) - ord('a')
        c2[pos]=c2[pos] + 1
        len_iter2=len_iter2 - 1
    len_iter3=len(c1)
    while len_iter3>0:
        num_of_list=len_iter3 - 1
        if c1[num_of_list] == c2[num_of_list]:
            pass
        else:
            print "Given strings are not anagrams"
            break
        len_iter3=len_iter3 - 1

if __name__=='__main__':
    validate_anagram()

########################## End of the Program