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
24 30

-----Sample Output-----
7

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

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