# Given a string 'str', this counts all substrings with length 2 and print them
def countsubstrings(str):
    for i in range(len(str)):
        substr = str[i:i+2] # substring with length 2

        # check if 'substr' is in count
        dict[substr] += 1

    return(dict)

if __name__ == '__main__':
    import sys
    str = sys.argv[1]
    # print str # for debug

    hash = countsubstrings(str)
    # print hash # for debug

    # sort dictionaries
    list = [ (k, hash[k]) for k in hash.keys() ]
    list.sort()
    list.reverse()

    # print all substrings
    for (v, k) in list:
        print k, " occurs ", v, " times"