c#include <bits/stdc++.h> using namespace std; int main() { cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(false); int N; cin >> N; int ans = 0; vector<int> arr(100, -1); for(int i = 0; i < N; i++){ int A, B; cin >> A >> B; if(arr[A] != -1 && arr[A] != B){ ans++; } arr[A] = B; } cout << ans << "\n"; return 0; }