A change-notification system models n components. A directed edge u v means a change in u triggers a re-evaluation of v. When component 0 changes, the trigger cascades along directed edges. Count how many distinct components (other than 0 itself) are eventually re-evaluated. The graph may contain cycles; each reachable component is counted once.

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).

Output format

A single integer: the number of distinct nodes reachable from node 0, excluding node 0.

Constraints

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

4 3
0 1
1 2
0 3

3

3 1
1 2

0