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 <stdio.h>
#include <map>
#include <algorithm>
using namespace std;

const int N = 123;

char a[N], b[N], c[N];

int calc(int idx) {
  map<char,int> mp;
  mp[a[idx]]++;
  mp[b[idx]]++;
  mp[c[idx]]++;
  int mx = -1;
  for (map<char,int>::iterator it = mp.begin(); it != mp.end(); it++) {
    mx = max(mx, it->second);
  }
  return 3 - mx;
}

int main() {
  int n;
  scanf("%d", &n);
  scanf("%s %s %s", a, b, c);
  int ans = 0;
  for (int i = 0; i < n; i++) {
    ans += calc(i);
  }
  printf("%d\n", ans);
  return 0;
}