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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            //[summary]A - Shiritori
            var lines = ReadLines<string>(1).ToList();

            if (IsShiritori(lines[0]))
            {
                Console.WriteLine("YES");
            }
            else
            {
                Console.WriteLine("NO");
            }            
        }

        static bool IsShiritori(List<string> line)
        {
            string s = "";

            foreach(var word in line)
            {
                if (s != "")
                {
                    if (!word.StartsWith(s))
                    {
                        return false;
                    }
                }

                s = word.Substring(word.Length - 1, 1);                
            }

            return true;
        }
                               
        static IEnumerable<List<T>> ReadLines<T>(int count = 0, char separator = ' ')
        {
            //[summary]コンソールの値を読み込んで、List<T>のコレクションを返却

            //読み込む行数が未指定のときは、1行目の値を"count"とみなす
            if (count == 0)
            {
                string line = Console.ReadLine().TrimEnd();
                count = int.Parse(line);
            }

            for (int i = 0; i < count; i++)
            {
                //コンソールを1行読み込み
                string line = Console.ReadLine().TrimEnd();

                //char型のときは1文字ずつに分割
                if (typeof(T) == typeof(char))
                {
                    var list = line.ToCharArray().ToList();
                    yield return (List<T>)(object)list;
                }
                else
                {
                    //読み込んだ値を"separator"で区切る
                    var list = line.Split(separator).ToList();

                    //int型のときは数値に変換
                    if (typeof(T) == typeof(int))
                    {
                        var numbers = list.ConvertAll(int.Parse);
                        yield return (List<T>)(object)numbers;
                    }
                    else if (typeof(T) == typeof(long))
                    {
                        var numbers = list.ConvertAll(long.Parse);
                        yield return (List<T>)(object)numbers;
                    }
                    else
                    {
                        yield return (List<T>)(object)list;
                    }
                }
            }
        }
    }
}