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;
using System.IO;

namespace ABC
{
    class ABC172B
    {
        const string FILE = "/tmp/data.txt";

        static void Main(string[] args)
        {
#if DEBUG
            Console.SetIn(new StreamReader(FILE));
#endif
            String s = Console.ReadLine();
            String t = Console.ReadLine();

            int c = 0;
            for (int i = 0; i < s.Length; ++i)
            {
                if (s[i] != t[i])
                {
                    ++c;
                }
            }

            Console.WriteLine(c);



#if DEBUG
            Console.WriteLine("*** end ***");
            Console.SetIn(Console.In);
            Console.ReadKey();
#endif
        }

        static long RL()
        {
            return long.Parse(Console.ReadLine());
        }

        static long[] RLa(long n)
        {
            string[] sa = Console.ReadLine().Split(' ');
            long[] la = new long[n];
            for (int i = 0; i < n; ++i)
            {
                la[i] = long.Parse(sa[i]);
            }
            return la;
        }
    }
}