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 PHP (5.6.30) (judge verdict: Accepted)

<?php
fscanf(STDIN, "%d", $n);
fscanf(STDIN, "%s", $a);
fscanf(STDIN, "%s", $b);
fscanf(STDIN, "%s", $c);
$m=0;
for($i=0;$i<$n;$i++){
  $j=0;
  $k=0;
  $l=0;
  (substr($a,$i,1)!=substr($b,$i,1))?$j++:"";
  (substr($b,$i,1)!=substr($c,$i,1))?$k++:"";
  (substr($c,$i,1)!=substr($a,$i,1))?$l++:"";
  if($j==0 && $k==0 && $l==0) continue;
  if($j==1 && $k==1 && $l==1) {$m=$m+2;continue;}
  if($j==1 && $k==1 && $l==0) {$m++;continue;}
  if($j==0 && $k==1 && $l==1) {$m++;continue;}
  if($j==1 && $k==0 && $l==1) {$m++;continue;}
}
echo $m."\n";
?>