problem88.cpp

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

class StrongestSecretPair {
  int n;
  vector<string> words;

public:
  void readInput() {
    cin >> n;
    cin.ignore();
    words.resize(n);
    for (int i = 0; i < n; ++i) {
      getline(cin, words[i]);
    }
  }

  void solve() {
    vector<pair<int, int>> masks; // {bitmask, length}

    for (string &word : words) {
      int mask = 0;
      for (char c : word) {
        mask |= (1 << (c - 'a'));
      }
      masks.push_back({mask, word.size()});
    }

    int maxStrength = 0;

    for (int i = 0; i < n; ++i) {
      for (int j = i + 1; j < n; ++j) {
        if ((masks[i].first & masks[j].first) == 0) {
          int strength = masks[i].second * masks[j].second;
          maxStrength = max(maxStrength, strength);
        }
      }
    }

    cout << maxStrength << endl;
  }
};

int main() {
  StrongestSecretPair solver;
  solver.readInput();
  solver.solve();
  return 0;
}