#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {

    int N;
    cin >> N;
    vector<int> kravi;
 for (int i = 0; i < N; i++) {
        int cnt, mleko;
        cin >> cnt >> mleko;

        for (int j = 0; j < cnt; j++) {
            kravi.push_back(mleko);
        }
    }
    sort(kravi.begin(), kravi.end());
    int vkkravi = kravi.size();
    int rez = 0;

    for (int i = 0; i < vkkravi / 2; i++) {
        int sega = kravi[i] + kravi[vkkravi - 1 - i];
        rez = max(rez, sega);
    }

    cout << rez << endl;

    return 0;
}