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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
$N = trim(fgets(STDIN));
$A = str_split(trim(fgets(STDIN)));
$B = str_split(trim(fgets(STDIN)));
$C = str_split(trim(fgets(STDIN)));
$ANS = 0;
for($i = 0;$i<$N;$i++){
 $ans = 0;
 $a = 0;
  $b = 0;
  $c = 0;
  if($A[$i]!=$B[$i]){
  ++$a;
  }
  if($A[$i]!=$C[$i]){
  ++$a;
  }
  $ans = $a;
  if($B[$i]!=$A[$i]){
++$b;
}
if($C[$i]!=$B[$i]){
++$b;
}
if($ans<$b){
$ans = $b;
}
    if($C[$i]!=$A[$i]){
++$c;
}
if($B[$i]!=$C[$i]){
++$c;
}
if($ans>$c){
$ans = $c;
}
$ANS += $ans;
}
echo $ANS;