import java.util.*;
import java.io.*;
import java.math.*;

class Main {

	public static void main(String[] args) throws IOException{
		Scanner sc = new Scanner(System.in);//new File("input.txt"));
	    PrintWriter pw = new PrintWriter(System.out);//new File("output.txt"));
      int n = sc.nextInt();
      int a[][] = new int[1005][1005];
      int ans = 0;
      for (int i = 0; i < 1000; i++)
    	  for (int j = 0; j < 1000; j++)
    		  a[i][j] = 0;
      for (int i = 0; i < n; i++)
      {
    	  int x1 = sc.nextInt();
    	  int y1 = sc.nextInt();
    	  int x2 = sc.nextInt();
    	  int y2 = sc.nextInt();
    	  for (int j = x1; j <= x2; j++)
    		  for (int k = y1; k <= y2; k++)
    			  a[j][k]++;
      }
      for (int i = 0; i <= 100; i++)
    	  for (int j = 0; j <= 100; j++)
    		  ans += a[i][j];
      pw.println(ans);
	   pw.close();
	}
}