// This is the text editor interface.
// Anything you type or change here will be seen by the other person in real time.
import java.util.*;
class Solution{
    public static void main(String[] str){
        List<int[]> list = new ArrayList<int[]>();
        list.add(new int[]{1,3,2});
        list.add(new int[]{2,4,2});
        //list.add(new int[]{5,6,7});
        //list.add(new int[]{5,8,2});
        System.out.println(String.valueOf(get_area(list)));
    }
    public static int get_area(List<int[]> list){
        if(list==null||list.size()==0) return 0;
        List<int[]> lines = new ArrayList<int[]>();
        for(int[] i : list){
            lines.add(new int[]{i[0],i[2]});
            lines.add(new int[]{i[1],-i[2]});
        }
        Collections.sort(lines,new Comparator<int[]>(){
            public int compare(int[] a, int[] b){
                if(a[0]!=b[0]) return a[0]-b[0];
                else return b[1]-a[1];
            }
        });
        PriorityQueue<Integer> height = new PriorityQueue<Integer>(100,Collections.reverseOrder());
        height.add(0);
        int pre = 0;
        List<int[]> point = new ArrayList<int[]>();
        for(int[] line:lines){
            if(line[1]>0){
                height.add(line[1]);
            }
            else{
                height.remove(-line[1]);
            }
            if(height.peek()!=pre){
                point.add(new int[]{line[0],height.peek()});
                pre = height.peek();
            }
        }
        int res = 0;
        for(int i =1;i<point.size();i++){
            int[] pre1 = point.get(i-1);
            int[] cur = point.get(i);
            res+=(cur[0]-pre1[0])*pre1[1];
        }
        return res;
    }
}