#include<iostream>
#include<cmath>
#include<bits/stdc++.h>
using namespace std;
struct cow{
	int x, y;
}a[100005];
bool cmp(cow a_x, cow a_y){
	return a_x.y > a_y.y;
}
int main(){
	int n;
	cin >> n;
	for(int i = 1; i <= n; i++)
		cin >> a[i].x >> a[i].y;
	sort(a+1, a+1+n, cmp);
	int s1 = 1, s2 = n;
	int ans = 0;
	for(int i = 1; i <= n; i++){
		int t = min(a[s1].x, a[s2].x);
		ans = max(ans, a[s1].y+a[s2].y);
		a[s1].x -= t, a[s2].x -= t;
		if(a[s1].x <= 0) s1++;
		if(a[s2].x <= 0) s2++;
	}
	cout << ans;
	return 0;
}