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 PHP (5.6.30) (judge verdict: Accepted)

<?php
// Try AtCoder
// author: Leonardone @ NEETSDKASU

function gets() { return trim(fgets(STDIN)); }
function geti() { return intval(gets()); }
function getVals() { return explode(' ', gets()); }
function getInts() { return array_map(intval, getVals()); }

$N = gets();

$ans = 0;

for ($i = 0; $i < $N; $i++) {
    list($li, $ri) = getInts();
    $ans += $ri - $li + 1;
}

echo $ans;