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)

/*
author : seryu
title : ABC172B_"Minor Change"
*/
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < n; i++)
#define reps(i,n) for(int i = 1; i <= n; i++)
#define rrep(i,n) for(int i = n-1; i >= 0; i--)
#define rreps(i,n) for(int i = n; i >= 1; i--)
#define mrep(i,j,n) for(int i = j; i < n; i++)
#define mreps(i,j,n) for(int i = j; i <= n; i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define ERASE(x,val) x.erase(remove(all(x), val), x.end())
#define MOD 1000000007
typedef long long ll;
typedef pair<int, int> P;
template<class T>inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; }return false; }

void solve()
{
	string s, t;
	cin >> s >> t;
	int ans = 0;
	rep(i, sz(s))
	{
		if(s[i] != t[i])ans++;
	}
	cout << ans << endl;
	return;	
}

int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}