#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); ++i)
using namespace std;
using ll=long long;
int main(){
    int x,y,z;
    cin>>x>>y>>z;
    int a=abs(x-y);
    if(a<=z)cout<<(x+y+z)/2<<endl;
    else cout<<min(x,y)+z<<endl;
}