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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

import Control.Applicative
import Control.Monad
import Data.List.Split

myRead :: String -> (Int, Int)
myRead s = (l, r)
    where
        [a, b] = splitOn " " s
        l = read a
        r = read b

solve :: [(Int, Int)] -> Int
solve = sum . ( map (\(l, r) -> r-l+1) )

main :: IO ()
main = do
    n <- read <$> getLine
    contents <- map myRead <$> replicateM n getLine
    print $ solve contents