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 Rust (1.15.1) (judge verdict: Wrong Answer)

use std::io;
use std::cmp;


fn main() {
    let n = read_one::<usize>();
    let a = read_one::<String>().chars().collect::<Vec<char>>();
    let b = read_one::<String>().chars().collect::<Vec<char>>();
    let c = read_one::<String>().chars().collect::<Vec<char>>();

    let mut ans;
    let mut cnt = 0;

    // a
    for i in 0..n {
        if a[i] != b[i] { cnt += 1; }
        if a[i] != c[i] { cnt += 1; }
    }

    ans = cnt;
    cnt = 0;

    // b
    for i in 0..n {
        if b[i] != a[i] { cnt += 1; }
        if b[i] != c[i] { cnt += 1; }
    }

    ans = cmp::min(ans, cnt);
    cnt = 0;

    // c
    for i in 0..n {
        if c[i] != a[i] { cnt += 1; }
        if c[i] != b[i] { cnt += 1; }
    }
    ans = cmp::min(ans, cnt);

    println!("{}", ans);
}


#[allow(dead_code)]
fn read<T>() -> Vec<T>
where T:
std::str::FromStr,
T::Err: std::fmt::Debug {

    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.split_whitespace()
        .map(|s| s.trim().parse().unwrap())
        .collect()
}

#[allow(dead_code)]
fn read_one<T>() -> T
where T:
std::str::FromStr,
T::Err: std::fmt::Debug {

    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.trim().parse().unwrap()
}