​#include <iostream>
using namespace std;
#include <iomanip>

int main ()
{
    int a, b, c;
    float medie;
    cin >> a >> b >> c;
    medie = (a + b + c) / 3.;
    medie = (int) (medie * 100)/100.;
    cout << fixed << setprecision(2) << medie;


    return 0;
}