#include<iostream>

using namespace std;

int main()
{
    double money[12],average=0;
    int index;
    for(index=0;index<12;index++)
    {
        cin>>money[index];
        average+=money[index];
    }
    average/=12;
    cout<<'$';
    cout.setf(ios::fixed);
    cout.setf(ios::showpoint);
    cout.precision(2);
    cout<<average<<endl;
    return 0;
}