#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <utility>
#include <cmath>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <numeric>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define exrep(i, a, b) for(ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll mod = 1000000007;
const ll INF = 1e16;
  
int main() {
    ll n, m;
    double p;
    cin >> n >> m >> p;

    double ans = 0.0;
    if(n == 1 && m == 1) {
        ans = p;
    }
    else if(n == 1) {
        ans = (2.0 + (m - 2) * p) * p * p;
    }
    else if(m == 1) {
        ans = (2.0 + (n - 2) * p) * p * p;
    }
    else {
        ans = (4.0 + 2.0 * (n + m - 4) * p + (n - 2) * (m - 2) * p * p) * p * p * p;
    }

    exout(ans);
    re0;
}