Problem:
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

Solution in JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input) {
    var input = input.split('\n');
    var n = parseInt(input[0], 10);
    var sum = 0;
    for(i = 1; i <= n; i++) {
      var a = input[i].split(' ').map(n => parseInt(n, 10));
      sum += a[1] - a[0] + 1;
    }
    console.log(sum);
 }
  Main(require('fs').readFileSync('/dev/stdin', 'utf8'));