Problem:
Score: 200 points

Problem Statement

We have a string S consisting of lowercase English letters.

If the length of S is at most K, print S without change.

If the length of S exceeds K, extract the first K characters in S, append ... to the end of them, and print the result.

Constraints

K is an integer between 1 and 100 (inclusive).

S is a string consisting of lowercase English letters.

The length of S is between 1 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

K
S

Output

Print a string as stated in Problem Statement.

Sample Input 1

7
nikoandsolstice

Sample Output 1

nikoand...

nikoandsolstice has a length of 15, which exceeds K=7.

We should extract the first 7 characters in this string, append ... to the end of them, and print the result nikoand....

Sample Input 2

40
ferelibenterhominesidquodvoluntcredunt

Sample Output 2

ferelibenterhominesidquodvoluntcredunt

The famous quote from Gaius Julius Caesar.

Solution in Rust (1.42.0) (judge verdict: Accepted)

use std::io;
use std::str;

pub struct Scanner<R> {
    reader: R,
    buffer: Vec<String>,
}

impl<R: io::BufRead> Scanner<R> {
    pub fn new(reader: R) -> Self {
        Scanner {
            reader: reader,
            buffer: Vec::new(),
        }
    }

    pub fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buffer.pop() {
                return token.parse().ok().expect("failed to parse token");
            }
            let mut input = String::new();
            self.reader.read_line(&mut input).expect("failed to read");
            self.buffer = input.split_whitespace().rev().map(String::from).collect();
        }
    }
}

use io::Write;
fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut stdout = io::BufWriter::new(stdout);
    let mut scanner = Scanner::new(stdin.lock());

    let k: usize = scanner.token();
    let mut s: Vec<char> = scanner.token::<String>().chars().collect();

    if s.len() > k {
        for i in 0..k {
            write!(&mut stdout, "{}", s[i]);
        }
        writeln!(&mut stdout, "...");
    } else {
        for x in s {
            write!(&mut stdout, "{}", x);
        }
        writeln!(&mut stdout, "");
    }
}