#include <iostream>
#include <algorithm>

int N;
int slot = 1, sum;
int a[2007], b[2007], n;
int s[2007], m;
int dp[2007][2007];

int main() {
  std::cin.tie(nullptr)->sync_with_stdio(false);
  std::cin >> N;
  while (N--) {
    int A, B;
    std::cin >> A >> B;
    if (A == 0) {
      if (B > 0) {
        s[++m] = B;
      }
    } else if (A == 1) {
      if (B > 0) {
        sum += B;
      }
    } else {
      if (B >= 0) {
        slot += A - 1, sum += B;
      } else {
        ++n, a[n] = A - 1, b[n] = -B;
      }
    }
  }
  for (int i = 1; i <= 2000; ++i) {
    dp[0][i] = +0x77359400;
  }
  for (int i = 1; i <= n; ++i) {
    for (int j = 0; j <= 2000; ++j) {
      dp[i][j] = dp[i - 1][j];
    }
    for (int j = a[i]; j <= 2000; ++j) {
      dp[i][j] = std::min(dp[i][j], dp[i - 1][j - a[i]] + b[i]);
    }
  }
  std::sort(s + 1, s + m + 1, std::greater<>());
  int ans = 0;
  for (int i = 0; i <= m; ++i) {
    sum += s[i];
    ans = std::max(ans, sum - dp[n][std::max(i - slot, 0)]);
  }
  std::cout << ans << '\n';
  return 0;
}