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.

4
west
east
wait

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.

9
different
different
different

0

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

7
zenkoku
touitsu
program

13