#include <iostream>
#include <iomanip>
#include <vector>
using namespace std ;
int n, m ;
double p ;
double f(double a, double b) {
   double d = abs(a-b) ;
   return min(a,b) + 0.25 * min(1., d * (2 - d)) ;
}
int main() {
   cin >> n >> m >> p ;
   vector<double> r(n) ;
   for (int i=0; i<n; i++)
      r[i] = 0.25 * i ;
   for (int j=0; j+1<m; j++) {
      r[0] += 0.25 ;
      for (int i=1; i<n; i++)
         r[i] = f(r[i-1], r[i]) ;
   }
   cout << setprecision(15) << r[n-1]*p << endl ;
}