#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

double solve(int n, int m, double p) {
  if (n < m) swap(n, m);

  if (n == 1) return p;

  double ret = 0.0;
  if (m == 1) {
    ret += 2 * p * p;
    ret += (n - 2) * p * p * p;
  } else {
    ret += 4 * p * p * p;
    ret += 2 * (n + m - 4) * p * p * p * p;
    ret += (n-2) * (m-2) * p * p * p * p * p;
  }

  return ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n, m;
  double p;
  cin >> n >> m >> p;
  cout << fixed << setprecision(10) << solve(n, m, p) << endl;
  
  return 0;
}