text: #include <bits/stdc++.h>
  using namespace std;
  
  double geometricDistribution(int n, double p)
  {
      return pow(1-p, n-1) * p;
  }
  
  int main(void)
  {
      int a, b, n;
      cin >> a >> b;
      cin >> n;
      double p = a * 1.0/b;
  
      double ans = 0.0;
      for(int i = 1; i <= n; i++){
          ans += geometricDistribution(i, p);
      }
  
      cout << fixed << setprecision(3) << ans << endl;
  
      return 0;
  }
  