import java.util.*;

import java.io.*;

public class crossroad {

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

try{

System.out.println("Starting");

BufferedReader f=new BufferedReader(new FileReader("crossroad.in"));

int N=Integer.parseInt(f.readLine());

int cows=10;

int[] Cows=new int[cows];

for(int i=0;i<cows;i++) {Cows[i]=0;}

int[] prev=new int[cows];

int id;

int pos;

for(int i=0;i<cows;i++) {prev[i]=-1;}

StringTokenizer st;

int total=0;

//int previd;

//previd=-1;

for(int i=0;i<N;i++) {

st=new StringTokenizer(f.readLine());

id=Integer.parseInt(st.nextToken())-1;

pos=Integer.parseInt(st.nextToken());

if(prev[id]!=pos) {

if(prev[id]==-1) {

prev[id]=pos;

}else {

Cows[id]++;

prev[id]=pos;

}

}

}

f.close();

for(int i=0;i<cows;i++) {

total=total+Cows[i];

}

try{

System.out.println("TRYING TO WRITE");

PrintWriter pw=new PrintWriter(new BufferedWriter(new FileWriter("crossroad.out")));

pw.println(total);

pw.close();

}catch(IOException e) {

System.out.println("File MISSING");

}

}catch(Exception e) {

System.out.println("ERROR:"+e.getMessage());

System.exit(1);

}

}

}