A company has n offices, numbered 1 to n, connected by a one-way phone tree: m directed links, where a link u v means office u can call office v directly (but not necessarily the reverse). An emergency alert starts at headquarters, office s, and propagates along the directed links: any office that receives the alert immediately relays it to every office it has a direct link to.

Report how many of the n offices NEVER receive the alert (office s itself always receives it, so it never counts as unreached).

Input format

Line 1: two integers n and m — number of offices (1-indexed) and number of links. Next m lines: two integers u v — a directed link from office u to office v. Last line: one integer s — the headquarters office.

Output format

A single integer: the number of offices that never receive the alert.

Constraints

• 1 ≤ n ≤ 40
• 0 ≤ m ≤ 200
• 1 ≤ u, v, s ≤ n

4 2
1 2
2 3
1

1

3 2
2 1
3 1
1

2