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 (GCC 9.2.1) (judge verdict: Accepted)

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) < (b) ? (a) : (b))

typedef long long int ll;

int read_int()
{
    int a;
    scanf("%d", &a);
    return a;
}

int read_lint()
{
    ll a;
    scanf("%lld", &a);
    return a;
}

int read_float()
{
    float a;
    scanf("%f", &a);
    return a;
}

int read_double()
{
    double a;
    scanf("%lf", &a);
    return a;
}

#define N 200001

char s[N], t[N];

int main()
{
    scanf("%s", &s);
    scanf("%s", &t);

    int ans = 0;
    for (int i = 0; i < N; i++)
    {
        if (s[i] == 0)
        {
            break;
        }
        if (s[i] != t[i])
        {
            ans++;
        }
    }
    printf("%d\n", ans);

    return 0;
}