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<bits/stdc++.h>
#define rep(i,n) for(int i=0;n>i;++i)
#define MOD 1000000007
using namespace std;
using ll=int64_t;
using pii=pair<int,int>;
using vi=vector<int>;
using VI=vector<ll>;
using vis=vector<string>;
using vvi=vector<vi>;
//最大公約数
int gcd(int a,int b){
    if(a%b==0)
    return b;
    return gcd(b,a%b);
}
//最小公倍数
int lcm(int a,int b){
   return a*b/gcd(a,b);
}
bool prime(int num){
    if (num < 2) return false;
    else if (num == 2) return true;
    else if (num % 2 == 0) return false;
    double sqrtNum = sqrt(num);
    for (int i = 3; i <= sqrtNum; i += 2){
        if (num % i == 0)
        return false;
    }
    return true;
}
int main(){
    string s,t;
    int ans=0;
    cin>>s>>t;
    for(int i=0;i<s.length();i++){
        if(s.compare(i,1,t,i,1)!=0)
        ans++;
    }
    cout<<ans<<endl;
}