mean.rs

use std::io::{stdin, BufRead};

type Number = i64;

fn main() {
    let mut nums: Vec<Number> = vec![];

    loop {
        if let Some(Ok(line)) = stdin().lock().lines().next() {
            if let Ok(num) = line.parse::<Number>() {
                nums.push(num);
            } else {
                break;
            }
        }
    }

    if !nums.is_empty() {
        println!("{}", nums.iter().sum::<Number>() as f64 / nums.len() as f64);
    }
}