#include<iostream>
using namespace std;
int main(){
    float q,w,e,r,t,y,u,i,o,p,a,s,d;
    cin>>q;cin>>w;
    cin>>e;
    cin>>r;
    cin>>t;
    cin>>y;
    cin>>u;
    cin>>i;
    cin>>o;
    cin>>p;
    cin>>a;
    cin>>s;
    d= (q+w+e+r+t+y+u+i+o+p+a+s)/12;
	printf("%.2lf", d);
	return 0;
}