#include <bits/stdc++.h>

using namespace std;

map<string, string> mapp;


int main() {
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        string s, ss;
        cin >> s >> ss;
        if (s.substr(0, 2) != ss)
            mapp.insert({s.substr(0, 2), ss});
    }

    int res = 0;
    for (pair<string, string> ele : mapp) {
        if (mapp[ele.second] == ele.first) {
            res++;
        }
    }
    cout << res / 2 << endl;
}