#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    vector < pair <int, int> > v;
    int cant, a, b, minimo = 0;

    cin >> cant;

    for(int i = 0; i < cant; i++)
    {
        cin >> a >> b;
        v.push_back({b, a});
    }

    sort(v.begin(), v.end());

    int i = 0, j = v.size()-1;
    while(i <= j)
    {
            minimo = max(minimo, (v[i].first + v[j].first));

            if(v[i].second > v[j].second)
            {
                v[i].second -= v[j].second;
                v[j].second = 0;
                j--;
            }
            else if(v[i].second < v[j].second)
            {
                v[j].second -= v[i].second;
                v[i].second = 0;
                i++;
            }
            else
            {
                v[j].second = 0;
                v[i].second = 0;
                i++;
                j--;
            }
    }

    cout << minimo << "\n";

    return 0;
}