## Description

Farmer John has returned to the County Fair so he can attend the
special events (concerts, rodeos, cooking shows, etc.). He wants
to attend as many of the N (1 <= N <= 10,000) special events as he
possibly can.

He's rented a bicycle so he can speed from one event to the next
in absolutely no time at all (0 time units to go from one event to
the next!).

Given a list of the events that FJ might wish to attend, with their
start times (1 <= T <= 100,000) and their durations (1 <= L <=
100,000), determine the maximum number of events that FJ can attend.
FJ never leaves an event early.

## Input

The input contains multiple test case, for each test case:

* Line 1: A single integer, N.

* Lines 2..N+1: Each line contains two space-separated integers, T and
L, that describe an event that FJ might attend.

## Output

For each test case:

* Line 1: A single integer that is the maximum number of events FJ can
attend.

## Sample Input

7
1 6
8 6
14 5
19 2
1 8
18 3
10 6

## Sample Output

4

## Source

U S OPEN, 2006 USACO Contest