#D7418. Reachability from the Capital
Reachability from the Capital
Reachability from the Capital
There are n cities and m roads in Berland. Each road connects a pair of cities. The roads in Berland are one-way.
What is the minimum number of new roads that need to be built to make all the cities reachable from the capital?
New roads will also be one-way.
Input
The first line of input consists of three integers n, m and s (1 ≤ n ≤ 5000, 0 ≤ m ≤ 5000, 1 ≤ s ≤ n) — the number of cities, the number of roads and the index of the capital. Cities are indexed from 1 to n.
The following m lines contain roads: road i is given as a pair of cities u_i, v_i (1 ≤ u_i, v_i ≤ n, u_i ≠ v_i). For each pair of cities (u, v), there can be at most one road from u to v. Roads in opposite directions between a pair of cities are allowed (i.e. from u to v and from v to u).
Output
Print one integer — the minimum number of extra roads needed to make all the cities reachable from city s. If all the cities are already reachable from s, print 0.
Examples
Input
9 9 1 1 2 1 3 2 3 1 5 5 6 6 1 1 8 9 8 7 1
Output
3
Input
5 4 5 1 2 2 3 3 4 4 1
Output
1
Note
The first example is illustrated by the following:
For example, you can add roads (6, 4), (7, 9), (1, 7) to make all the cities reachable from s = 1.
The second example is illustrated by the following:
In this example, you can add any one of the roads (5, 1), (5, 2), (5, 3), (5, 4) to make all the cities reachable from s = 5.
inputFormat
Input
The first line of input consists of three integers n, m and s (1 ≤ n ≤ 5000, 0 ≤ m ≤ 5000, 1 ≤ s ≤ n) — the number of cities, the number of roads and the index of the capital. Cities are indexed from 1 to n.
The following m lines contain roads: road i is given as a pair of cities u_i, v_i (1 ≤ u_i, v_i ≤ n, u_i ≠ v_i). For each pair of cities (u, v), there can be at most one road from u to v. Roads in opposite directions between a pair of cities are allowed (i.e. from u to v and from v to u).
outputFormat
Output
Print one integer — the minimum number of extra roads needed to make all the cities reachable from city s. If all the cities are already reachable from s, print 0.
Examples
Input
9 9 1 1 2 1 3 2 3 1 5 5 6 6 1 1 8 9 8 7 1
Output
3
Input
5 4 5 1 2 2 3 3 4 4 1
Output
1
Note
The first example is illustrated by the following:
For example, you can add roads (6, 4), (7, 9), (1, 7) to make all the cities reachable from s = 1.
The second example is illustrated by the following:
In this example, you can add any one of the roads (5, 1), (5, 2), (5, 3), (5, 4) to make all the cities reachable from s = 5.
样例
5 4 5
1 2
2 3
3 4
4 1
1