#include<stdio.h>
#include<algorithm>
using namespace std;
struct xy {	int x, y;}a[121212];
bool sort_y(xy a, xy b) {
	if (a.y != b.y)return a.y < b.y;
	return a.x < b.x;
}
int max(int a, int b) { if (a < b)return b; return a; }
int main() {
	int n, i;
	scanf("%d", &n);
	for (i = 0; i < n; i++) {
		scanf("%d%d", &a[i].x, &a[i].y);
	}
	sort(a, a + n,sort_y);
	int p1 = 0, p2 = n - 1;
	int ans = 0;
	while (p1 <= p2) {
		ans = max(ans, a[p1].y + a[p2].y);
		if (a[p1].x == a[p2].x) p1++, p2--;
		else if (a[p1].x < a[p2].x) a[p2].x -= a[p1++].x;
		else a[p1].x -= a[p2--].x;
	}
	printf("%d", ans);
	return 0;
}

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MwoxIDgKMiA1CjEgMg==

3
1 8
2 5
1 2