Tulips

There are 15,000 known kinds of tulips in Byteland, and each kind has been assigned a single catalogue number between 1 and 15,000. Byteasar has kept his own private tulip index for many years.

The board of directors of the Botanic Garden believes that gathering every kind of tulip in one place would greatly increase the garden's popularity. They want to know how many kinds of tulips are still missing from the garden.

The kinds of tulips growing in each bed of the garden have already been identified. Determine how many kinds of tulips the board still has to buy in order to have every kind of tulip in the garden.

The first line contains the number of beds in the garden, $n$ ($1 \le n \le 20000$). The second line contains $n$ integers, each in the range $[1, 15000]$, giving the catalogue number of the kind of tulip growing in each bed.

Print a single integer on one line: the number of kinds of tulips the board has to buy in order to have every kind of tulip in the garden.