#include 
     
      #include 
      
       #include 
       
        using namespace std;double Out,a[10],ans;int main(){    cin>>a[1]>>a[2]>>a[3]>>a[4]>>a[5]>>a[6]>>a[7];    ans = a[1]+a[2]+a[3]+a[4]+a[5]+a[6]+a[7];    Out = 5040 * a[1]/ans * a[2] /(ans-1) * a[3] /(ans-2) * a[4] /(ans-3) * a[5] /(ans-4) * a[6] /(ans-5) * a[7];     printf("%.3lf",Out);    return 0;}