content: package v104;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  public class CowsAndCars_UVa10491 {
  
      public static void main(String[] args) throws IOException {
      
          Scanner sc = new Scanner(System.in);
          PrintWriter out = new PrintWriter(System.out);
  
          while(sc.ready())
          {
          	double cows = sc.nextInt(), cars = sc.nextInt(), tot = cows + cars, shows = sc.nextInt();
              out.printf("%.5f\n", cars*(cars-1) / (tot*(tot-shows-1)) + cows*cars / (tot*(tot-shows-1)));
          }
          out.flush();
          out.close();
      }
      
  
      static class Scanner 
      {
          StringTokenizer st;
          BufferedReader br;
  
          public Scanner(InputStream s){  br = new BufferedReader(new InputStreamReader(s));}
  
          public String next() throws IOException 
          {
              while (st == null || !st.hasMoreTokens()) 
                  st = new StringTokenizer(br.readLine());
              return st.nextToken();
          }
          
          public int nextInt() throws IOException {return Integer.parseInt(next());}
  
          public long nextLong() throws IOException {return Long.parseLong(next());}
  
          public String nextLine() throws IOException {return br.readLine();}
  
          public boolean ready() throws IOException {return br.ready(); }
  
  
      }
      
  }