100731: [AtCoder]ABC073 B - Theater

Problem Statement

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.

Sample Input 1

1
24 30

Sample Output 1

7

There are $7$ people, sitting at Seat $24,25,26,27,28,29$ and $30$.

Sample Input 2

2
6 8
3 3

Sample Output 2

4