#include<map>  
#include<set>  
#include<list>  
#include<cmath>  
#include<ctime>  
#include<deque>  
#include<stack>  
#include<bitset>  
#include<cstdio>  
#include<vector>  
#include<cstdlib>  
#include<cstring>  
#include<iomanip>  
#include<numeric>  
#include<sstream>  
#include<utility>  
#include<iostream>  
#include<algorithm>  
#include<functional>  
  
using namespace std ;  
  
int main()  
{  
    double cow , car , door ;  
    while( cin >> cow >> car >> door )  
        cout << setprecision( 5 ) << fixed << ( cow + car - 1 ) * car / (( cow + car ) * ( cow + car - door - 1 ) ) << endl ;  
    return 0;  
}