#include <cmath>
#include <iomanip>
#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n, m, p;
  cin >> n >> m >> p;
  vector<vector<double>> dp(2);
  for(auto& x: dp) x.resize(m);
  for(int j = 1; j < m; j++) dp[0][j] = j/4.;
  for(int i = 1; i < n; i++) {
    dp[i%2][0] = i/4.;
    for(int j = 1; j < m; j++) {
      double lhs = dp[i%2][j-1];
      double rhs = dp[(i%2)^1][j];
      double diff = rhs - lhs;
      dp[i%2][j] = (lhs+rhs)/2-diff*diff/4;
    }
  }
  cout << fixed << setprecision(39) << (p*dp[1^(n%2)][m-1]) << "\n";
}