citystate.java

import java.io.*;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.StringTokenizer;
import java.util.*;
class stuff {
    String city;
    String state;
}
public class citystate {
    public static void main(String[] args) throws IOException {
        // write your code here
        BufferedReader br = new BufferedReader(new FileReader("citystate.in"));
        PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("citystate.out")));
        int n = Integer.parseInt(br.readLine());
        Map<String, Long> count = new HashMap<String, Long>();
        for(int i = 0; i < n; i++) {
            StringTokenizer st = new StringTokenizer(br.readLine());
            String city = st.nextToken();
            String state = st.nextToken();
            if(!city.substring(0, 2).equals(state)) {
                String key = city.substring(0, 2) + state;
                if(!count.containsKey(key)) {
                    count.put(key, 0L);
                }
                count.put(key, count.get(key) + 1);
            }
        }
        long ret = 0;
        for(String key: count.keySet()) {
            String otherKey = key.substring(2) + key.substring(0, 2);
            if(count.containsKey(otherKey)) {
                ret += count.get(key) * count.get(otherKey);
            }
        }
        // note that we have double-counted each pair
        pw.println(ret / 2);
        pw.close();


    }
}