#include <bits/stdc++.h>
using namespace std;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  long long n, m;
  cin >> n >> m;
  double p;
  cin >> p;
  if (n > m) {
    swap(n, m);
  }
  vector<long long> c(5);
  if (n == 1) {
    if (m == 1) {
      c[0] = 1;
    } else {
      c[1] = 2;
      c[2] = m - 2;
    }
  } else {
    c[2] = 4;
    c[3] = 2 * (n + m - 4);
    c[4] = n * m - c[2] - c[3];
  }
  double res = 0;
  for (int x = 0; x <= 4; ++x) {
    res += c[x] * pow(p, x + 1);
  }
  cout << fixed << setprecision(15) << res << '\n';
}