fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).unwrap();
    let n: i32 = n.trim().parse().unwrap();
    
    let zeta = |x| {
    	let mut ans = 0f64;
    	for i in (1..=100).rev() {
    		ans += (1. / i as f64).powi(x);
    	}
    	ans
    };
	
	println!("{}", zeta(n));
}