#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
    float a[5];
    int i = 0;
    float sum = 0;
    float aver = 0;
    cout.setf(ios::fixed);
    for(i = 0; i<6; i++)
    {
        cin>>a[i];
        sum += a[i];
    }
    aver = sum/5;
    cout<<fixed<<setprecision(2)<<aver;
    return 0;
}