Problem:
Score : 200 points

Problem Statement

You are given three strings A, B and C. Each of these is a string of length N consisting of lowercase English letters.

Our objective is to make all these three strings equal. For that, you can repeatedly perform the following operation:

Operation: Choose one of the strings A, B and C, and specify an integer i between 1 and N (inclusive). Change the i-th character from the beginning of the chosen string to some other lowercase English letter.

What is the minimum number of operations required to achieve the objective?

Constraints

1 \leq N \leq 100

Each of the strings A, B and C is a string of length N.

Each character in each of the strings A, B and C is a lowercase English letter.

Input

Input is given from Standard Input in the following format:

N
A
B
C

Output

Print the minimum number of operations required.

Sample Input 1

4
west
east
wait

Sample Output 1

3

In this sample, initially A = west、B = east、C = wait. We can achieve the objective in the minimum number of operations by performing three operations as follows:

Change the second character in A to a. A is now wast.

Change the first character in B to w. B is now wast.

Change the third character in C to s. C is now wast.

Sample Input 2

9
different
different
different

Sample Output 2

0

If A, B and C are already equal in the beginning, the number of operations required is 0.

Sample Input 3

7
zenkoku
touitsu
program

Sample Output 3

13

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<numeric>
#include<math.h>
using namespace std;
typedef long long ll;
ll MOD = 1e9+7;
#define rep(i,n) for(int i = 0; i < (n); ++i)
int main() {
    int n;
    cin >> n;
    string a, b, c;
    cin >> a >> b >> c;
    int ans = 0;
    rep(i, n) {
        if ( a[i] == b[i] && b[i] == c[i] ) {
            continue;
        }
        else if ( a[i] == b[i] || b[i] == c[i] || a[i] == c[i] ) {
            ++ans;
        }
        else {
            ans += 2;
        }
    }
    cout << ans << endl;
    return 0;
}