#include <iostream>
#include <cmath>
#include <string>
#include <algorithm>
#include <vector>

using namespace std;


int main()
{
    string s;
    getline(cin, s);

    vector<long long> a;

    for (long long i = 0; i < s.length(); ++i) {
        if (s[i] != ' ') {
            if (s[i] == '-') {
                i++;
                int t = 0;

                while (s[i] >= '0' && s[i] <= '9')  {
                    t = t*10 + s[i] - '0';
                    i++;
                }
                a.push_back(-t);

            } else {
                int t = 0;

                while (s[i] >= '0' && s[i] <= '9')  {
                    t = t*10 + s[i] - '0';
                    i++;
                }
                a.push_back(t);
            }
        }
    }

    /*for (int i = 0; i < a.size(); ++i) {
        cout << a[i] << " ";
    } cin.get();*/

    long long max1 = -10000000, min1 = 10000000;
    for (long long i = 0; i < a.size(); ++i) {
        if ( (i+1) % 2 == 0 ) {
            if (a[i] > max1) max1 = a[i];
        } else {
            if (a[i] < min1) min1 = a[i];
        }
    }
    cout << max1 + min1;

    return 0;
}