Problem:
Score : 400 points

Problem Statement

We have a permutation of the integers from 1 through N, p_1, p_2, .., p_N.
We also have M pairs of two integers between 1 and N (inclusive), represented as (x_1,y_1), (x_2,y_2), .., (x_M,y_M).
AtCoDeer the deer is going to perform the following operation on p as many times as desired so that the number of i (1 ≤ i ≤ N) such that p_i = i is maximized:

Choose j such that 1 ≤ j ≤ M, and swap p_{x_j} and p_{y_j}.

Find the maximum possible number of i such that p_i = i after operations.

Constraints

2 ≤ N ≤ 10^5

1 ≤ M ≤ 10^5

p is a permutation of integers from 1 through N.

1 ≤ x_j,y_j ≤ N

x_j ≠ y_j

If i ≠ j, \{x_i,y_i\} ≠ \{x_j,y_j\}.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
p_1 p_2 .. p_N
x_1 y_1
x_2 y_2
:
x_M y_M

Output

Print the maximum possible number of i such that p_i = i after operations.

Sample Input 1

5 2
5 3 1 4 2
1 3
5 4

Sample Output 1

2

If we perform the operation by choosing j=1, p becomes 1 3 5 4 2, which is optimal, so the answer is 2.

Sample Input 2

3 2
3 2 1
1 2
2 3

Sample Output 2

3

If we perform the operation by, for example, choosing j=1, j=2, j=1 in this order, p becomes 1 2 3, which is obviously optimal.
Note that we may choose the same j any number of times.

Sample Input 3

10 8
5 3 6 8 7 10 9 1 2 4
3 1
4 1
5 9
2 5
6 5
3 5
8 9
7 9

Sample Output 3

8

Sample Input 4

5 1
1 2 3 4 5
1 5

Sample Output 4

5

We do not have to perform the operation.

Solution in Ruby (2.7.1) (judge verdict: Accepted)

class DisjointSet
	def initialize(n)
		@parent = Array.new(n){-1}
	end
	def find(a)
		return a if @parent[a]<0
		@parent[a] = find(@parent[a])
	end
	def union(a, b)
		x = find(a)
		y = find(b)
		return x if x == y
		if size(x) < size(y)
			t = x
			x = y
			y = t
		end
		@parent[x] += @parent[y]
		@parent[y] = x
		x
	end
	def size(a)
		-@parent[find(a)]
	end
end

N,M=gets.split.map(&:to_i)
P=gets.split.map{|i|i.to_i-1}
set=DisjointSet.new(N)
M.times{
	x,y=gets.split.map{|i|i.to_i-1}
	set.union(x,y)
}
warn set.inspect
c=0
N.times{|i|
	if set.find(P[i]) == set.find(i)
		warn [i,P[i]].inspect
		c+=1
	end
}
puts c