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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

using static System.Math;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            //var line = ReadLine().Split(' ').Select(value => long.Parse(value)).ToArray();
            //var a = long.Parse(ReadLine());
            var s = ReadLine();
            var t = ReadLine();

            var count = 0;
            for(var i = 0; i < s.Length; i++)
            {
                if(s[i] != t[i])
                {
                    count++;
                }
            }
            
            WriteLine(count);
        }
    }
}