use std::io::Read;

fn solve(nm: Vec<u64>, p: f64) {
    let n = nm[0];
    let m = nm[1];
    if n > 1 && m > 1 {
        let corners: f64 = 4f64 * p * (p * p);
        let edges: f64 = (((2*n + 2*m) as f64) - 8f64) * p * (p * p * p);
        let inners: f64 = (((n - 2) * (m - 2)) as f64) * p * (p * p * p * p);
        println!("{}", corners + edges + inners);
    } else if n > 1 || m > 1 {
        let corners: f64 = 2f64 * p * (p);
        let edges: f64 = (((n * m) as f64) - 2f64) * p * (p * p);
        println!("{}", corners + edges);
    } else {
        println!("{}", p);
    }
}

fn main() {
    let mut all_data = String::new();
    std::io::stdin().read_to_string(&mut all_data).ok();
    let all_data: Vec<&str> = all_data.trim().split('\n').map(|s| s.trim()).collect();
    let nm: Vec<u64> = all_data.iter().next().unwrap().split_whitespace().map(|b| b.parse::<u64>().unwrap()).collect();
    let p: f64 = all_data.iter().skip(1).next().unwrap().parse::<f64>().unwrap();
    solve(nm, p);
}