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 LuaJIT (2.0.4) (judge verdict: Accepted)

local ior = io.input()
local n, m = ior:read("*n", "*n")

local parent = {}
local groupsize = {}
for i = 1, n do parent[i] = i end
for i = 1, n do groupsize[i] = 1 end

local function getroot(idx)
  while(parent[idx] ~= idx) do
    idx = parent[idx]
  end
  return idx
end

for i = 1, m do
  local x, y, z = ior:read("*n", "*n", "*n")
  local xroot, yroot = getroot(x), getroot(y)
  if(groupsize[xroot] < groupsize[yroot]) then
    groupsize[yroot] = groupsize[xroot] + groupsize[yroot]
    parent[x] = yroot
    parent[xroot] = yroot
    parent[y] = yroot
  else
    groupsize[xroot] = groupsize[xroot] + groupsize[yroot]
    parent[x] = xroot
    parent[yroot] = xroot
    parent[y] = xroot
  end
end
local grouplist = {}
local cnt = 0
for i = 1, n do
  local r = getroot(i)
  if(grouplist[r] == nil) then
    grouplist[r] = true
    cnt = cnt + 1
  end
end
print(cnt)