#include <bits/stdc++.h> using namespace std; constexpr int N = 1e5+5; namespace trie { struct Node { int val; Node *nxt[26]; Node() { val = 0; for (int i = 0; i < 26; ++i) nxt[i] = nullptr; } } *root = new Node(); int id; int get(string s) { Node *cur = root; for (char c : s) { int idx = c - 'a'; if (!cur->nxt[idx]) cur->nxt[idx] = new Node(); cur = cur->nxt[idx]; } if (cur->val) return cur->val; return cur->val = ++id; } } int n; int p[N]; bool mark[N]; int dfs(int v) { mark[v] = true; int res = 1; if (!mark[p[v]]) res += dfs(p[v]); return res; } signed main() { cin.tie(0)->sync_with_stdio(0); cin >> n; bool sub3 = true; for (int i = 1; i <= n; ++i) { string s, t; cin >> s >> t; int si = trie::get(s), ti = trie::get(t); p[si] = ti; sub3 = sub3 && si == ti; } if (n % 2 == 1) { cout << -1; return 0; } if (sub3) { cout << n; return 0; } int res = 0; for (int i = 1; i <= n; ++i) { if (!mark[i]) { int val = dfs(i); if (val == 2) continue; res += val / 2 + val % 2; } } cout << res; }