Problem:
Score : 100 points

Problem Statement

You are given three strings A, B and C. Check whether they form a word chain.

More formally, determine whether both of the following are true:

The last character in A and the initial character in B are the same.

The last character in B and the initial character in C are the same.

If both are true, print YES. Otherwise, print NO.

Constraints

A, B and C are all composed of lowercase English letters (a - z).

1 ≤ |A|, |B|, |C| ≤ 10, where |A|, |B| and |C| are the lengths of A, B and C, respectively.

Input

Input is given from Standard Input in the following format:

A B C

Output

Print YES or NO.

Sample Input 1

rng gorilla apple

Sample Output 1

YES

They form a word chain.

Sample Input 2

yakiniku unagi sushi

Sample Output 2

NO

A and B form a word chain, but B and C do not.

Sample Input 3

a a a

Sample Output 3

YES

Sample Input 4

aaaaaaaaab aaaaaaaaaa aaaaaaaaab

Sample Output 4

NO

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

io = STDIN
n,ww=io.gets.chomp.split.map(&:to_i)
hash=Hash.new{|h,k|h[k]=[]}
n.times do
  w,v=io.gets.chomp.split.map(&:to_i)
  hash[w]<<v
end
hash.keys.each do |k|
  hash[k].sort!.reverse!
end
hh={}
hash.each do |k,v|
  hh[k]=v.size
end
ans=0
keys=hh.keys
(0..hh[keys[0]]).each do |i|

  (0..hh[keys[1]]).each do |j|
    (0..hh[keys[2]]).each do |k|
      if (keys[0]*i + keys[1]*j + keys[2]*k) <= ww
         sum=0
         s=hash[keys[0]][0,i].inject(:+)
         sum+=s if s
         s=hash[keys[1]][0,j].inject(:+)
         sum+=s if s
         s=hash[keys[2]][0,k].inject(:+)
         sum+=s if s
         ans=[ans,sum].max
      end
    end if keys.size==3
  end if keys.size>=2
end if keys.size>=1
p ans