#include <bits/stdc++.h>
using namespace std;
const int MAXN = 132674;
const int MOD = 1e9 + 7;
int main() {
  set<int> ar;
  set<int> to_buy;
  set<int> to_sell;
  long long multiplyier = 1;
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int temp;
    string l;
    cin >> l;
    scanf("%d", &temp);
    if (l.size() == 3) {
      if (to_buy.size() > 0 && *to_buy.rbegin() > temp) {
        to_buy.insert(temp);
      } else if (to_sell.size() > 0 && *to_sell.begin() < temp) {
        to_sell.insert(temp);
      } else
        ar.insert(temp);
    } else {
      if (ar.find(temp) != ar.end()) {
        for (auto u : ar) {
          if (u != temp) {
            if (u < temp)
              to_buy.insert(u);
            else
              to_sell.insert(u);
          }
        }
        ar.clear();
        multiplyier = (multiplyier * 2) % MOD;
      } else if (to_buy.find(temp) != to_buy.end()) {
        if (*to_buy.rbegin() != temp) {
          cout << 0;
          return 0;
        }
        to_buy.erase(temp);
        for (auto u : ar) to_sell.insert(u);
        ar.clear();
      } else if (to_sell.find(temp) != to_sell.end()) {
        if (*to_sell.begin() != temp) {
          cout << 0;
          return 0;
        }
        to_sell.erase(temp);
        for (auto u : ar) to_buy.insert(u);
        ar.clear();
      }
    }
  }
  cout << (multiplyier * ((int)ar.size() + 1)) % MOD;
  return 0;
}
