#include <bits/stdc++.h>

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define ll long long

using namespace std;

const int N = 500100;
int n;
int T[N];
ll V[N];

namespace brut {
  const int MAXN = 4010;
  ll dp[MAXN][2];
  multiset <ll> ms;

  ll brut1() {
    ll out = 0;
    REP(i, MAXN) dp[i][0] = dp[i][1] = -(1LL << 60);
    dp[0][0] = 0;

    REP(i, n) {
      int t = T[i];
      ll v = V[i];

      REP(j, n) {
        dp[j][1] = dp[j][0];
        if (t == 2 && j > 0) dp[j][1] = max(dp[j][1], dp[j - 1][0] - v);
        if (t == 1)          dp[j][1] = max(dp[j][1], dp[j + 1][0] + v);

        out = max(out, dp[j][1]);
      }

      REP(j, n) dp[j][0] = dp[j][1];
    }

    return out;
  }

  /*ll brut2() {
    ll out = 0;

    REP(i, n) {
      int t = T[i];
      ll v = V[i];

      if (t == 1) {
        if (ms.empty()) continue;

        ll curr = *ms.begin();
        if (curr < v) {
          out += v - curr;
          ms.erase(ms.begin());
        }
      } else {
        ms.insert(v);
      }
    }

    return out;
  }*/

  /*ll init() {
    if (n <= 2000) return brut1();
    else           return brut2();

    return -1;
  }*/
}

namespace solution {
  multiset <ll> a, b;

  ll init() {
    a.clear();
    b.clear();
    ll out = 0;

    REP(i, n) {
      int t = T[i];
      ll v = V[i];

      if (t == 1) {
        if (a.size() == 0 || (*a.begin()) >= v) {
          if (b.size() == 0 || (*b.begin()) >= v) continue;

          out += v - (*b.begin());
          b.erase(b.begin());
          b.insert(v);
        } else {
          if (b.size() == 0 || (*a.begin()) <= (*b.begin())) {
            out += v - (*a.begin());
            a.erase(a.begin());
            b.insert(v);
          } else {
            out += v - (*b.begin());
            b.erase(b.begin());
            b.insert(v);
          }
        }
      } else {
        a.insert(v);
      }
    }

    return out;
  }
}

/*namespace generator {
  void init() {
    n = rand() % 300 + 1700;
    int l1 = rand() * rand() % 10000 + 1, l2 = rand() * rand() % 10000 + 1;
    REP(i, n) {
      T[i] = (rand() & 1) + 1;
      if (T[i] == 1) V[i] = rand() * rand() % l1;
      else           V[i] = rand() * rand() % l2;
    }
    return;
  }
}*/

/*namespace testing {
  void init() {
    srand(time(0));

    int cnt = 0;
    ll A = 0, B = 0;
    while (A == B) {
      generator::init();
      cout << n << " " << cnt << endl;
      A = brut::init(), B = solution::init();

      if (A != B) {
        cout << n << "\n";
        REP(i, n) {
          cout << T[i] << " " << V[i] << "\n";
        }
        cout << A << " " << B << "\n";
      }

      cout << A << " " << B << endl << endl;
      cnt++;

      assert(A == B);
    }

    return;
  }
}*/

int main() {
  ios_base::sync_with_stdio(false);

  //testing::init();

  cin >> n;
  REP(i, n) cin >> T[i] >> V[i];
  if (n <= 2000) cout << brut::brut1() << "\n";
  else           cout << solution::init() << "\n";

  return 0;
}