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: Runtime Error)

using System;
class Code_01
{
    public static void Main()
    {
        string Datas1 = Console.ReadLine();
        bool OK = false;
        if (Datas1.Length != 1)
        {
            for (int i = 0; i < Datas1.Length; i++)
            {
                string s1 = Datas1.Substring(i, 1);
                if (s1 == "h")
                {
                    string s2 = Datas1.Substring(i + 1, 1);
                    if (s2 == "i")
                    {
                        OK = true;
                    }
                }
            }
        }
       
        if (OK)
        {
            Console.WriteLine("Yes");
        }
        else
        {
            Console.WriteLine("No");
        }

    }
}