Theater

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

inputFormat

input values are integers.

Input

Input is given from Standard Input in the following format:

N l_1 r_1 : l_N r_N

outputFormat

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

样例

1
24 30

7