You invited n guests to dinner! You plan to arrange one or more circles of chairs. Each chair is going to be either occupied by one guest, or be empty. You can make any number of circles. 

Your guests happen to be a little bit shy, so the i-th guest wants to have a least l_i free chairs to the left of his chair, and at least r_i free chairs to the right. The "left" and "right" directions are chosen assuming all guests are going to be seated towards the center of the circle. Note that when a guest is the only one in his circle, the l_i chairs to his left and r_i chairs to his right may overlap.

What is smallest total number of chairs you have to use?

Input

First line contains one integer n — number of guests, (1 ⩽ n ⩽ 10^5). 

Next n lines contain n pairs of space-separated integers l_i and r_i (0 ⩽ l_i, r_i ⩽ 10^9).

Output

Output a single integer — the smallest number of chairs you have to use.

Examples

Input

3
1 1
1 1
1 1


Output

6


Input

4
1 2
2 1
3 5
5 3


Output

15


Input

1
5 6


Output

7

Note

In the second sample the only optimal answer is to use two circles: a circle with 5 chairs accomodating guests 1 and 2, and another one with 10 chairs accomodationg guests 3 and 4.

In the third sample, you have only one circle with one person. The guest should have at least five free chairs to his left, and at least six free chairs to his right to the next person, which is in this case the guest herself. So, overall number of chairs should be at least 6+1=7.

import java.io.OutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;
//import java.math.*;
 
/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
 
public class Main {
	
	static int MD= 998244353 ;
	static int N=300000;
    public static void main(String[] args) throws IOException {
    	OutputStream outputStream = System.out;
        InputReader in = new InputReader();
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }
   

	static class TaskC {
    	 
	    public void solve(int testNumber, InputReader in, PrintWriter out) throws IOException {
	    	 
	    	int t=1;
	    	while(t-->0) { 
	    		int n=in.nextInt();
	    		int[] l=new int[n];
	    		int[] r=new int[n];
	    		for(int i=0;i<n;i++) {
	    			l[i]=in.nextInt();
	    			r[i]=in.nextInt();
	    		}
	    		sort(l,0,n);
	    		sort(r,0,n);
	    		long ans=n;
	    		for(int i=0;i<n;i++) {
	    			ans+=Math.max(l[i], r[i]);
	    		}
	    		out.println(ans);
	    			
	    			
	    	}
	    }
	    	
	}
	   
	
    
    static long modexp(long x, long n) 
    { 
        if (n == 0) { 
            return 1; 
        } 
        else if (n % 2 == 0) { 
            return modexp((x * x) % MD, n / 2); 
        } 
        else { 
            return (x * modexp((x * x) % MD, (n - 1) / 2) % MD); 
        } 
    } 
      
     static long getInv(long b) 
    { 
      
        long  d = modexp(b, MD - 2); 
      
        long ans =  (d % MD) ;
      
        return ans; 
    } 
    
    static class InputReader
    {
        BufferedReader br;
        StringTokenizer st;
 
        public InputReader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
 
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
   
        int nextInt()
        {
            return Integer.parseInt(next());
        }
 
        long nextLong()
        {
            return Long.parseLong(next());
        }
 
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
 
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    
    }
    static void sort(int[] a, int low, int high) 
    {
        int N = high - low;         
        if (N <= 1) 
            return; 
        int mid = low + N/2; 
        sort(a, low, mid); 
        sort(a, mid, high); 
        int[] temp = new int[N];
        int i = low, j = mid;
        for (int k = 0; k < N; k++) 
        {
            if (i == mid)  
                temp[k] = a[j++];
            else if (j == high) 
                temp[k] = a[i++];
            else if (a[j]<a[i]) 
                temp[k] = a[j++];
            else 
                temp[k] = a[i++];
        }    
        for (int k = 0; k < N; k++) 
            a[low + k] = temp[k];         
    }
    static void lsort(long[] a, int low, int high) 
    {
        int N = high - low;         
        if (N <= 1) 
            return; 
        int mid = low + N/2; 
        lsort(a, low, mid); 
        lsort(a, mid, high); 
        long[] temp = new long[N];
        int i = low, j = mid;
        for (int k = 0; k < N; k++) 
        {
            if (i == mid)  
                temp[k] = a[j++];
            else if (j == high) 
                temp[k] = a[i++];
            else if (a[j]<a[i]) 
                temp[k] = a[j++];
            else 
                temp[k] = a[i++];
        }    
        for (int k = 0; k < N; k++) 
            a[low + k] = temp[k];         
    }
    public static long fexp(long x, long y, long p) {
        long res = 1;      
        
       
        x = x % p;  
      
        while (y > 0) 
        { 
         
            if((y & 1)==1) 
                res = (res * x) % p; 
      
          
            y = y >> 1;  
            x = (x * x) % p;  
        } 
        return res; 
        
    }
    static int gcd(int a, int b) 
    { 
        if (b == 0) 
            return a; 
        return gcd(b, a % b);  
          
    }
    static long lgcd(long a, long b) 
    { 
        if (b == 0) 
            return a; 
        return lgcd(b, a % b);  
          
    }
   
	
	
}
 
