#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
void debug_(auto s, auto ...a) {
  cerr << "\e[1;32m(" << s << ") = (";
  int f = 0;
  (..., (cerr << (f++ ? ", " : "") << a));
  cerr << ")\e[0m\n";
}
#include <experimental/iterator>
void orange_(auto s, auto L, auto R) {
  cerr << "\e[1;33m[ " << s << " ] = [ ";
  using namespace experimental;
  copy(L, R, make_ostream_joiner(cerr, ", "));
  cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  int tot = 0;
  map<pair<string, string>, int> a;
  for (int i = 0; i < n; ++i) {
    string s, o;
    int x;
    cin >> s >> o >> x;
    a[{s, o}] += x;
    tot += x;
  }
  map<string, int> b;
  for (auto [k, v] : a) {
    auto [s, o] = k;
    if (o == "any")
      v = min(v, 1);
    b[s] = max(b[s], v);
  }
  int ans = 1;
  for (auto [k, v] : b)
    ans += v;
  if (ans > tot) {
    cout << "impossible\n";
  } else {
    cout << ans << '\n';
  }
  return 0;
}