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;
using System.Linq;

namespace Hitachi2020A
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            string s = Console.ReadLine();
            string res = "Yes";
            if (s.Length < 2)
            {
                Console.WriteLine("No");
                return;
            }
            for (int i = 0; i < s.Length; i++)
            {
                if (s.Substring(i,2) == "hi")
                {
                    i++;
                    continue;
                }
                else
                {
                    res = "No";
                    break;
                }
            }
            Console.WriteLine(res);
        }
    }
}