#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define PI 3.1415926535
#define bp __builtin_popcount
ll mod=1000000007;
int main()
{
    int x,y,z;
    cin>>x>>y>>z;
    if(x==y)
        cout<<x+(z/2)<<endl;
    else
    {
        if(x<y)
        {
            if(z>=y-x)
            {
                z-=(y-x);
                x=y;
                cout<<x+(z/2)<<endl;
            }
            else
            {
                x+=z;
                cout<<x<<endl;
            }
        }
        else
        {
            if(z>=x-y)
            {
                z-=(x-y);
                y=x;
                cout<<x+(z/2)<<endl;
            }
            else
            {
                y+=z;
                cout<<y<<endl;
            }
        }
    }
}