Joisino is working as a receptionist at a theater.

The theater has 100000 seats, numbered from 1 to 100000.

According to her memo, N groups of audiences have come so far, and the i-th group occupies the consecutive seats from Seat l_i to Seat r_i (inclusive).

How many people are sitting at the theater now?

Constraints

* 1≤N≤1000
* 1≤l_i≤r_i≤100000
* No seat is occupied by more than one person.
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
l_1 r_1
:
l_N r_N


Output

Print the number of people sitting at the theater.

Examples

Input

1
24 30


Output

7


Input

2
6 8
3 3


Output

4
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int count = 0;

		int chair[][] = new int[n][2];

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

			for (int j = 0; j < 2; j++) {
				chair[i][j] = sc.nextInt();
			}

			count += chair[i][1] - chair[i][0] + 1;
		}
		System.out.println(count);

	}

}
