use std::cmp::min;

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: u128 = n.trim().parse().unwrap();

    let mut max_val = 0u128;
    while 2u128.pow(max_val as u32) < n {
        max_val += 1;
    }
    let limit = 2 * max_val;
    let mut result: usize = 2 * max_val as usize;
    for j in 3..=limit {
        for i in 0.. {
            if (j as u128).pow(i as u32) > n {
                result = min(result, j as usize * i as usize);
                break;
            }
        }
    }
    println!("{}", result);
}