#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;

int main() {

  int n, m;
  cin >> n >> m;
  ld p;
  cin >> p;
  if (n > m) swap(n, m);
  ld res = 0;
  if (n == 1) {
    if (m == 1) res = p;
    else res = p * p * 2 + p * p * p * (m - 2);
  } else {
    res = p * p * p * 4 + p * p * p * p * 2 * (n + m - 4) + p * p * p * p * p * (n - 2) * (m - 2);
  }
  printf("%.12Lf\n", res);
  return 0;
}