Problem:
Score : 200 points

Problem Statement

Given are strings S and T. Consider changing S to T by repeating the operation below. Find the minimum number of operations required to do so.

Operation: Choose one character of S and replace it with a different character.

Constraints

S and T have lengths between 1 and 2\times 10^5 (inclusive).

S and T consists of lowercase English letters.

S and T have equal lengths.

Input

Input is given from Standard Input in the following format:

S
T

Output

Print the answer.

Sample Input 1

cupofcoffee
cupofhottea

Sample Output 1

4

We can achieve the objective in four operations, such as the following:

First, replace the sixth character c with h.

Second, replace the eighth character f with t.

Third, replace the ninth character f with t.

Fourth, replace the eleventh character e with a.

Sample Input 2

abcde
bcdea

Sample Output 2

5

Sample Input 3

apple
apple

Sample Output 3

0

No operations may be needed to achieve the objective.

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

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

namespace ConsoleApplication6
{

    class Program
    {
        static void Main(string[] args)
        {
            var S = RL();
            var T = RL();
            var ret = 0;
            var length=S.Length;

            for (int i = 0; i < length; i++)
            {
                if (S[i] != T[i]) ret++;
            }
               
            Console.WriteLine(ret);
            Console.ReadLine();

        }

        static IEnumerable<int> RL2IE() { return spr(RL()).Select(x => (int)c2i(x)); }
        static string RL() { return Console.ReadLine().Trim(); }
        static IEnumerable<string> spr(string s) { return s.Split(' '); }
        static Int64 c2i(string c) { return Int64.Parse(c); }
        //static double c2d(string c) { return double.Parse(c); }
        static string bool2ret(bool b) { return b ? "Yes" : "No"; }
    }
}