Simple Temperature Converter in Rust

main.rs

use std::io;
use std::io::Write;

fn main() {
    println!("Welcome to the temperature converter!");
    
    'program: loop {        
        println!("--------------------");
        println!("Enter 1 for °F ➔ °C.");
        println!("Enter 2 for °C ➔ °F.");
        println!("Enter 3 to QUIT.");

        'converter: loop {
            let mut input = String::new();
            io::stdin()
                .read_line(&mut input)
                .expect("Failed to read line.");

            let input: i32 = input.trim()
                .parse()
                .expect("Input not an integer.");

            if input == 1 {
                print!("°F: ");
                io::stdout().flush().unwrap();
                let mut fahr = String::new();
                io::stdin()
                    .read_line(&mut fahr)
                    .expect("Failed to read line.");
                let fahr: f32 = fahr.trim()
                    .parse()
                    .expect("Input not an integer.");
                let cels: f32 = convert_to_cels(fahr);
                println!("It is {cels} °C.");
                break 'converter;
            }
            else if input == 2 {
                print!("°C: ");
                io::stdout().flush().unwrap();
                let mut cels = String::new();
                io::stdin()
                    .read_line(&mut cels)
                    .expect("Failed to read line.");
                let cels: f32 = cels.trim()
                    .parse()
                    .expect("Input not an integer.");
                let fahr: f32 = convert_to_fahr(cels);
                println!("It is {fahr} °F.");
                break 'converter;
            }
            else if input == 3 {
                break 'program;
            }
            else {
                println!("Options: 1, 2, 3.");
            }
        }
    }
    println!("Goodbye!");
}   

fn convert_to_cels(fahr: f32) -> f32 {
    (fahr - 32.0) * (5.0 / 9.0)
}

fn convert_to_fahr(cels: f32) -> f32 {
    (cels * (9.0 / 5.0)) + 32.0
}