Problem:
Score : 200 points

Problem Statement

Find the largest square number not exceeding N. Here, a square number is an integer that can be represented as the square of an integer.

Constraints

1 \leq N \leq 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the largest square number not exceeding N.

Sample Input 1

10

Sample Output 1

9

10 is not square, but 9 = 3 × 3 is. Thus, we print 9.

Sample Input 2

81

Sample Output 2

81

Sample Input 3

271828182

Sample Output 3

271821169

Solution in Rust (1.15.1) (judge verdict: Runtime Error)

use std::io::prelude::*;
use std::io::stdin;
use std::str::FromStr;

fn main() {
    let s: Vec<char> = read::<String>().chars().collect();
    let t: Vec<char> = read::<String>().chars().collect();
    println!(
        "{}",
        if s[0] == t[2] && s[1] == t[1] && s[2] == t[0] {
            "YES"
        } else {
            "NO"
        }
    );
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let token: String = stdin
        .lock()
        .bytes()
        .map(|b| b.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}