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 JavaScript (node.js v5.12) (judge verdict: Runtime Error)


var input = require('fs').readFileSync('/dev/stdin', 'utf8');

var list = input.split(' ');

var n = Number(list[0]);

var a = list[1].split('');

var b = list[2].split('');

var c = list[3].split('');

var num = 0;

var getIndex = (i)  => {
  if (a[i] === b[i] || b[i] === c[i] || c[i] === a[i]) {
    return true;
  }
  return false;
}

for (var j = 0; j < n; j++) {
  if (!getIndex(j)) {
    num += 2;
  } else if (a[j] === b[j] && b[j] === c[j]) {
  } else {
    num += 1;
  }
}

console.log(num);