/* -*- coding: utf-8 -*-
 *
 * 959.cc:  No.959 tree and fire - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

ll nbrs[5];

/* subroutines */

/* main */

int main() {
  int n, m;
  double p;
  scanf("%d%d%lf", &n, &m, &p);

  if (n > m) swap(n, m);

  if (n == 1) {
    if (m == 1) nbrs[0] = 1;
    else {
      nbrs[1] = 2;
      nbrs[2] = m - 2;
    }
  }
  else {
    nbrs[2] = 4;
    nbrs[3] = (ll)((n - 2) + (m - 2)) * 2;
    nbrs[4] = (ll)(n - 2) * (m - 2);
  }

  double sum = 0.0, ep = p;
  for (int i = 0; i <= 4; i++, ep *= p)
    sum += ep * nbrs[i];

  printf("%.10lf\n", sum);
  return 0;
}