Problem:
Score : 100 points

Problem Statement

A Hitachi string is a concatenation of one or more copies of the string hi.

For example, hi and hihi are Hitachi strings, while ha and hii are not.

Given a string S, determine whether S is a Hitachi string.

Constraints

The length of S is between 1 and 10 (inclusive).

S is a string consisting of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S is a Hitachi string, print Yes; otherwise, print No.

Sample Input 1

hihi

Sample Output 1

Yes

hihi is the concatenation of two copies of hi, so it is a Hitachi string.

Sample Input 2

hi

Sample Output 2

Yes

Sample Input 3

ha

Sample Output 3

No

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

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


class Program
{
    static void Main(string[] args)
    {
        // 入力
        var s = Console.ReadLine();
        //var n = int.Parse(Console.ReadLine());
        //int[] n = Console.ReadLine().Split().Select(int.Parse).ToArray();

        var ans = "No";
        var h = false;
        var i = false;
        var end = false;
        for (int k = 0; k < s.Length; k++)
        {
            if (!h && !i && !end)
            {
                if (s[k] == 'h') h = true;
                else
                {
                    h = false;
                    i = false;
                    end = false;
                }
            }
            else if (h && !i && !end)
            {
                if (s[k] == 'i') i = true;
                else
                {
                    h = false;
                    i = false;
                    end = false;
                }
            }
            else if (h && i && !end)
            {
                if (s[k] != 'i') end = true;
                else
                {
                    h = false;
                    i = false;
                    end = false;
                }
            }


            if (h && i && end)
            {
                ans = "Yes";
                break;
            }
        }

        if (h && i)
        {
            ans = "Yes";
        }

        // 出力
        Console.WriteLine(ans);
    }
}