#include<iostream>
using namespace std;
main()
{
	int a,b,c;cin>>a>>b>>c;
	if(a>b)a^=b^=a^=b;
	if(b-a>c)
	{
		cout<<a+c<<endl;
	}
	else
	{
		cout<<b+(c-b+a)/2<<endl;
	}
}