#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <tuple>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <cmath>
#include <iomanip>
#define rep(i, n) for(int i = 0; i < (int)(n); ++i)
using namespace std;

int main(void) {
    cout << fixed << setprecision(15);
    
    int N, M;
    long double P;
    cin >> N >> M >> P;
    if (N > M) swap(N, M);
    if (N == 1) {
        if (M == 1) cout << P << endl;
        else cout << P * P * 2 + P * P * P * (M - 2) << endl;
    } else {
        cout << P * P * P * 4 + P * P * P * P * (2 * N + 2 * M - 8) + P * P * P * P * P * (N - 2) * (M - 2) << endl;
    }
    return 0;
}