import java.awt.List;
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int q = in.nextInt();
        int len = 0;
        for(int a0 = 0; a0 < q; a0++){
            len = in.nextInt();
            int c = in.nextInt();
            // your code goes here
        }
        int[] len_elements = new int[len];
        for(int i=0;i<len;i++){
        	len = len_elements[i];
        	len--;
        }
        lena_sort(len_elements);
        
    }
    public static int lena_sort(int[] len_elements){
    	 if(len_elements.length <= 1){
         	System.out.println("1");
         }
         int pivot = len_elements[0];
         int[] less = new int[1000];
         int[] more = new int[1000];
         int j=0,m=0;
         for(int i=1;i<len_elements.length;i++){
         	if(len_elements[i] < pivot){
         		len_elements[i] = less[j];
         		j++;
         	}
         	else{
         		len_elements[i] = more[j];
         		m++;
         	}
         }
         int sorted_less = lena_sort(less);
         int sorted_more = lena_sort(more);
         int ans = sorted_less + pivot + sorted_more;
    	return ans;
    }
}