#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    int n,i;
    float a,s;
    s=0;
    for(i=1;i<=12;i++)
    {
        cin>>a;
        s=s+a;
    }
    printf("$%0.2f",s/12);
}