#include<bits/stdc++.h>  
const int inf = 0x3f3f3f3f;
using namespace std;
struct ITEM{
	int hk, v;
}a[2010]; int sza;
int b[2010], s[2010]; int szb;
int n;
int anssum, anscnt;
int f[2010];
bool cmp1(const int A, const int B) {return A > B; }
void input(){
	anssum = 1;
	int x, y;
	scanf("%d", &n);
	for(int i = 1; i <= n; ++ i){
		scanf("%d%d", &x, &y);
		if(x == 0){
			if(y <= 0) -- i, -- n;
			else ++ szb, b[szb] = y;
		}
		else{
			if(y >= 0) anssum += x-1, anscnt += y;
			else ++ sza, a[sza].hk = x-1, a[sza].v = y;
		}
	}
	anssum = min(anssum, n);
}
void ss(){
	for(int i = 0; i <= 2000; ++ i)f[i] = -inf;
	for(int i = 0; i <= anssum; ++ i)f[i] = 0;
	for(int i = 1; i <= sza; ++ i)
		for(int j = 2000; j >= a[i].hk; -- j)f[j] = max(f[j], f[j-a[i].hk] + a[i].v);
	for(int i = n - 1; i >= 0; -- i)f[i] = max(f[i], f[i+1]);
	sort(b + 1, b + 1 + szb, cmp1);
	for(int i = 1; i <= 2000; ++ i)s[i] = s[i-1] + b[i];
	int ans = 0;
	for(int i = 0; i <= 2000; ++ i){
		ans = max(ans, f[i]+s[i]);
	}
	printf("%d\n", ans+anscnt);
}
int main(){
	input();
	ss();
	return 0;
}