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.