#include<bits/stdc++.h> using namespace std; int main() { int a,b,c; cin>>a>>b>>c; double ans=(a+b+c)/3.0; printf("%.3lf",ans); return 0; }

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b>>c;
	double ans=(a+b+c)/3.0;
	printf("%.3lf",ans);
	return 0;
}

#include<bits/stdc++.h> using namespace std; int main() { int a,b,c; cin>>a>>b>>c; printf("%.3f",double(a+b+c)/3);

return 0;

}