use proconio::input;

fn main() {
    input! {
        n: usize,
    }

    let m = (n as f64).sqrt() as usize;

    println!(
        "{}",
        if m * m > n {
            m - 1
        } else if (m + 1) * (m + 1) <= n {
            m + 1
        } else {
            m
        }
    );
}