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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program ABC_073_B_Theater
   implicit none
   integer N, i
   integer, allocatable :: l(:), r(:)
   read(*, *) N
   allocate(l(1: N))
   allocate(r(1: N))
   do i = 1, N
       read(*, *) l(i), r(i)
   end do
   write(*, *) sum(r - l) + N
end program ABC_073_B_Theater