the length of the string entered by the user is too large by two

Question

I'm trying to learn Rust then I make a little game to practice.

The goal of the game is simple. Chose a letter and if the letter is not in the word, you lose a life. You must discover the word.

There is my code:

use std::io::{stdin};
use rand::Rng;

fn main() {
    let array_mot_pendu = ["trotinette", "pendu", "ravioli"];

    let mut rng = rand::thread_rng();

    let mot_a_deviner = array_mot_pendu[rng.gen_range(0..array_mot_pendu.len())];
    println!("{}", mot_a_deviner);

    let mut d = ['_'; 5];
    d[0] = mot_a_deviner.chars().nth(0).unwrap();
    
    println!("{:?}", d);
    let ch = mot_a_deviner.chars().nth(0).unwrap();
    
    
    println!("Bienvenue dans ce pendu! Vous avez 5 vies pour deviner le mot affiché. Si vous vous trompez vous perdez une vie.");

    let mut input_string = String::new();
    stdin().read_line(&mut input_string)
        .ok()
        .expect("ERREUR");

    let cha = input_string.chars().nth(0).unwrap();
    println!("?{}", cha);

    loop {
    if input_string.len() == 1 {
        println!("ah")

        // if input_string.is_alphabetic() {
        //     break
        // }
    //     }
    //     else:
    //     println!("Erreur, choisissez une lettre");
    //     let mut input_string = String::new();
        }
    }

}

The problem is that the length of the string is greater than two, but I can't display it. Is it like in C, or is there a "\n" behind it? I couldn't find anything on it.

When I put this

    println!("{}", input_string.chars().count());

It gives me my string +2 characters

(If you have a better solution for specifying that the string must be a char better than if input_string.len() == 1 I welcome the answer.)