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: Accepted)

fn main() {
    solve_b();
}
fn solve_b() {
    let mut buf = String::new();
    let handle = std::io::stdin();
    let n: usize = {
        handle.read_line(&mut buf).unwrap();
        let tmp = buf.trim().parse().unwrap();
        buf.clear();
        tmp
    };
    let mut a: String = {
        handle.read_line(&mut buf).unwrap();
        let tmp = buf.trim().parse().unwrap();
        buf.clear();
        tmp
    };
    let mut b: String = {
        handle.read_line(&mut buf).unwrap();
        let tmp = buf.trim().parse().unwrap();
        buf.clear();
        tmp
    };
    let mut c: String = {
        handle.read_line(&mut buf).unwrap();
        let tmp = buf.trim().parse().unwrap();
        buf.clear();
        tmp
    };
    let mut sum = 0;
    for i in 0..n {
        sum += b_diff(a.pop().unwrap(), b.pop().unwrap(), c.pop().unwrap());
    }
    println!("{}", sum);
}
fn b_diff(a: char, b: char, c: char) -> usize {
    if a == b && b == c {
        return 0;
    } else if a == b || b == c || c == a {
        return 1;
    } else {
        return 2;
    }
}


fn solve_a() {
    let mut buf = String::new();
    let handle = std::io::stdin();
    let config: Vec<usize> = {
        handle.read_line(&mut buf).unwrap();
        let tmp = buf
            .trim()
            .split_whitespace()
            .map(|a| a.parse().unwrap())
            .collect();
        buf.clear();
        tmp
    };
    let mut max;
    let mut min;
    if config[1] + config[2] > config[0] {
        min = config[1] + config[2] - config[0];
    } else {
        min = 0
    }
    max = {
        if config[1] < config[2] {
            config[1]
        } else {
            config[2]
        }
    };
    println!("{} {}", max, min);
}