#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll mod=1000000007;
ll inf=10099999999999990;
int main(){
    vector<ll>a(3);
    for (ll i = 0; i < 3; i++)
    {
        cin >> a[i];
    }
    ll left=0,right=inf;
    sort(a.begin(),a.end());
    while (right-left>1)
    {
        ll mid=(right+left)/2;
        bool ok=false;
        if (mid<=a[0])
        {
            ok=true;
        }
        ll x=mid-a[0];
        ll y=a[1]-a[0];
        ll z=a[2]-a[0];
        if (y>=x)
        {
            ll w=max(0LL,y-x)/2+max(0LL,z-x)/2;
            if (w>=x)
            {
                ok=true;
            }
        }else{
            x+=mid-a[1];
            if ((a[2]-mid)/2>=x)
            {
                ok=true;
            }
        }
        if (ok)
        {
            left=mid;
        }else{
            right=mid;
        }
    }
    cout << left << endl;
}