#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <complex>
using namespace std;

typedef long long ll;
typedef uint64_t ull;
typedef pair<int, int> P;
constexpr double PI = 3.1415926535897932;   // acos(-1)
constexpr double EPS = 1e-9;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    using ld = long double;
    int n, m;
    ld p;
    cin >> n >> m >> p;
    cout << fixed << setprecision(10);
    if(n == 1 && m == 1){
        cout << p << endl;
        return 0;
    }
    if(n > m)   swap(n, m);
    if(n == 1){
        ld ans = 2.0 * p * p;
        ans += p * p * p * (m - 2);
        cout << ans << endl;
        return 0;
    }
    
    ld ans = 4.0 * p * p * p;
    ans += 2.0 * (n + m - 4) * p * p * p * p;
    ans += p * p * p * p * p * (n - 2) * (m - 2);
    cout << ans << endl;
}