import re
import sys
from collections import defaultdict

wordsInOrder = []
for line in sys.stdin:
    wordsInOrder.extend( re.findall(r'\w+', line.lower()) )

single = defaultdict(int) 
double = defaultdict(int) 
triple = defaultdict(int)

for i, word in enumerate(wordsInOrder):
    single[word] += 1
    try:
        next_word = wordsInOrder[i+1]
        double[word + ' ' + next_word] += 1

        next_next_word = wordsInOrder[i+2]
        triple[word + ' ' + next_word + ' ' + next_next_word] += 1
    except:
        pass

def sort_by_frequency(d):
    return sorted(d.iterkeys(), cmp = lambda x,y: cmp(d[y], d[x]))

for singlet in sort_by_frequency(single):
    print singlet
    for doublet in sort_by_frequency(double):
        if not doublet.startswith(singlet + ' '):
            continue
        print "\t", doublet
        for triplet in sort_by_frequency(triple):
            if not triplet.startswith(doublet + ' '):
                continue
            print "\t\t", triplet