#include <iostream>
#include<iomanip>
using namespace std;
int main()
{ unsigned x,y,z;
cin>>x>>y>>z;
if(x>10||y>10||z>10)
{ cout<<"Nota maxima e 10, deci nu merge";
}
else
if(x<=10&&y<=10&&z<=10)
{ cout << setprecision(3) << fixed << (x + y + z) / 3.f << "\b ";
}
return 0;}