A task graph has n tasks. A directed edge u v means task u must be completed before task v. Given a target task t, count how many distinct tasks are ancestors of t — that is, tasks from which t is reachable by following directed edges (not counting t itself). These are exactly the tasks that must be finished, directly or transitively, before t can run. The graph may contain cycles.

Input format

Line 1: two integers n and m — the number of nodes (labeled 0 through n-1) and the number of directed edges. Each of the next m lines: two integers u v, a directed edge from u to v (read as: u must come before v). The final line: a single integer t, the target task.

Output format

A single integer: the number of distinct nodes from which t is reachable, excluding t.

Constraints

• 1 <= n <= 30
• 0 <= m <= 200
• 0 <= u, v <= n-1, 0 <= t <= n-1 (cycles and self-loops may appear)

4 3
0 1
1 2
3 2
2

3

3 1
0 1
0

0