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<iostream>
#include<cmath>
#include<string>
#include<cstdlib>
#include<ctime>

using namespace std;

#define MODULE 1
#define RAND(min,max) (rand()%(max-min+1)+min)
#define LOG(log) cout<<#log<<" : "<<log<<endl;
#define DEBUG() {cout<<"DEBUG "<<num_debug<<endl; num_debug++;}
int num_debug = 0;

int compare_int(void* a, void* b);
class Math {
public :
	template<typename T> static T P(int n, int r) {
		T ans = 1;
		for (int i = 0; i < r; i++) {
			ans *= n - i;
		}
		return ans;
	}
public:
	template<typename T>static T C(int n, int r) {
		T nmr = 1;
		T dnm = 1;
		if (n - r < r)
			r = n - r;
		for (int i = 0; i < r; i++) {
			nmr *= n - i;
			dnm *= r - i;
		}
		return nmr / dnm;
	}
};

int main(void) {
	srand((unsigned)time(NULL));
	
	char c;
	string S, T;
	cin >> S;
	//LOG(S.length());

	cin >> T;

	int dif = 0;
	for (int k = 0; k < S.length(); k++) {
		if (S[k] != T[k]) {
			dif++;
		}
	}
	//DEBUG();

	cout << dif;

	return 0;
}

int compare_int(void* a, void* b) {
	return *(int*)a;
}