Workout Intensity Progression Count

A fitness-tracking app assigns every logged workout an integer intensity rating. Analysts consider a logged workout to be part of a progression if there exists some other logged workout, anywhere in the log and not necessarily adjacent to it, whose intensity rating is exactly one greater. Every entry in the log is checked independently, so if the same rating value appears multiple times and it has a qualifying successor rating somewhere in the log, every one of those repeated entries counts separately.

Given the full list of logged intensity ratings, in the order they were logged, report how many logged entries are part of a progression.

Input format

• Line 1: an integer n, the number of logged workouts.
• Line 2: n space-separated integers, the intensity ratings, in the order they were logged.

Output format

Print a single integer: the number of entries x in the log for which the value x + 1 also appears somewhere in the log.

Constraints

• 1 <= n <= 1000
• 0 <= rating <= 1000

3
1 2 3

2

3
1 1 2

2