Contest Duration: - (local time) (100 minutes) Back to Home
B - Theater /

Time Limit: 2 sec / Memory Limit: 256 MB

### 問題文

joisinoお姉ちゃんは、劇場の受付を担当しています。

この劇場には、席 1 から席 100000 までの、100000 個の席があります。

### 制約

• 1≦N≦1000
• 1≦l_i≦r_i≦100000
• 同じ席に複数の人が座ることはない。
• 入力は全て整数である。

### 入力

N
l_1 r_1
:
l_N r_N


### 入力例 1

1
24 30


### 出力例 1

7


24,25,26,27,28,29,30 番の席に人が座っており、 7 人です。

### 入力例 2

2
6 8
3 3


### 出力例 2

4


Score : 200 points

### 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