#include <iostream>
#include <iomanip>
using namespace std;
int main(){
double balance;
double totalbalance=0;
for(int i=0;i<12;i++){
cin>>balance;
totalbalance+=balance;
}
cout<<setiosflags(ios::fixed)<<setprecision(2)<<"$"<<totalbalance/12;
return 0;
}
