#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll dp[2005];
const ll inf = 1e18;
int main () {
int n;
cin >> n;
vector<ll> cand;
for (int i = 2; i <= 2000; i++) dp[i] = -inf;
while (n--) {
int a, b;
cin >> a >> b;
if (a) for (int i = 2000; i > 0; i--) dp[i] = max(dp[i], dp[max(0, i-a)+1] + b);
else if (b >= 0) cand.push_back(b);
}
sort(cand.rbegin(), cand.rend());
int sz = cand.size();
for (int i = 1; i < sz; i++) cand[i] += cand[i-1];
ll ans = 0;
if (!cand.empty()) for (int i = 0; i < 2000; i++) ans = max(ans, dp[i+1] + cand[min(i, sz-1)]);
cout << ans << '\n';
return 0;
}
