use proconio::input;

fn main() {
    input! {
        n: u64,
    }

    println!("{}", u64_floor_sqrt(n));
}

// https://rsk0315.hatenablog.com/entry/2023/11/07/221428
// big 感謝...
fn u64_floor_sqrt(n: u64) -> u64 {
    let tmp = (n as f64).sqrt() as u64;
    let tmp_m1 = tmp.saturating_sub(1);
    if tmp_m1 * (tmp_m1 + 2) < n { tmp } else { tmp_m1 }
}