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: Accepted)

use std::io::*;

fn read() -> String {
    let s = stdin();
    let b = s.bytes()
        .map(|c| c.unwrap() as char)
        .take_while(|c| !c.is_whitespace())
        //.collect::<Vec<char>>();
		.collect::<String>();
	b
}

fn main() {
	let n = read().parse::<u64>().unwrap();
	let ch = false;
	let mut b = 1;
	let mut bb = 1;

	while bb <= n {
		b += 1;
		bb = b * b;
	}
	println!("{}", (b - 1) * (b - 1));
}