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

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