use std::io::Read;

fn run() {
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let n: u64 = it.next().unwrap().parse().unwrap();
    let m: u64 = it.next().unwrap().parse().unwrap();
    let p: f64 = it.next().unwrap().parse().unwrap();
    let (h, w) = (std::cmp::min(n, m), std::cmp::max(n, m));
    let ans = if w == 1 {
        p
    } else if h == 1 {
        2.0 * p.powi(2) + (w - 2) as f64 * p.powi(3)
    } else {
        4.0 * p.powi(3) + 2.0 * (h + w - 4) as f64 * p.powi(4) + (h - 2) as f64 * (w - 2) as f64 * p.powi(5)
    };
    println!("{:.8}", ans);
}

fn main() {
    run();
}