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

int main() {
    int n;
    cin >> n;
    vector<int> vec;
    long long sum = 0;
    while (n--) {
        int a, b;
        cin >> a >> b;
        if (b == 0) sum += a;
        else vec.push_back(a);
    }
    sort(vec.begin(), vec.end());
    for (int i = vec.size() - 1; i >= 0; i--) {
        if (vec[i] > sum) sum+=vec[i];
        else sum *= 2;
    }
    cout << sum << endl;
}