Problem:
Score : 500 points

Problem Statement

There are N cards placed face down in a row. On each card, an integer 1 or 2 is written.

Let A_i be the integer written on the i-th card.

Your objective is to guess A_1, A_2, ..., A_N correctly.

You know the following facts:

For each i = 1, 2, ..., M, the value A_{X_i} + A_{Y_i} + Z_i is an even number.

You are a magician and can use the following magic any number of times:

Magic: Choose one card and know the integer A_i written on it. The cost of using this magic is 1.

What is the minimum cost required to determine all of A_1, A_2, ..., A_N?

It is guaranteed that there is no contradiction in given input.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq X_i < Y_i \leq N

1 \leq Z_i \leq 100

The pairs (X_i, Y_i) are distinct.

There is no contradiction in input. (That is, there exist integers A_1, A_2, ..., A_N that satisfy the conditions.)

Input

Input is given from Standard Input in the following format:

N M
X_1 Y_1 Z_1
X_2 Y_2 Z_2
\vdots
X_M Y_M Z_M

Output

Print the minimum total cost required to determine all of A_1, A_2, ..., A_N.

Sample Input 1

3 1
1 2 1

Sample Output 1

2

You can determine all of A_1, A_2, A_3 by using the magic for the first and third cards.

Sample Input 2

6 5
1 2 1
2 3 2
1 3 3
4 5 4
5 6 5

Sample Output 2

2

Sample Input 3

100000 1
1 100000 100

Sample Output 3

99999

Solution in Lua (5.3.2) (judge verdict: Accepted)

--
local N, M = io.read("n", "n")

-- from ABC120
local parents = {}
for i=1,N do
    parents[i] = -1
end
local function find_root(x)
    while parents[x] > 0 do
        x = parents[x]
    end
    return x
end
local function find_union(a, b, update)
    local x, y = a, b
    while parents[x] > 0 do
        x = parents[x]
    end
    while parents[y] > 0 do
        y = parents[y]
    end
    local size_a, size_b = -parents[x], -parents[y]
    if update and x ~= y then
        if size_b > size_a then
            x, y = y, x
        end
        -- size(x) > size(y)
        -- x is new root of y
        parents[x] = parents[x] + parents[y]
        parents[y] = x
    end
    return x == y, size_a, size_b
end

for i=1,M do
    local a,b,z = io.read("n", "n", "n")
    find_union(a,b,true)
end

local set = {}
for i=1,N do
    local r = find_root(i)
    set[r] = true
end
local count = 0
for _ in pairs(set) do
    count = count + 1
end
print(count)