# 11724번 연결 요소의 개수 S2

from collections import deque 

def bfs(start_node, graph):
    queue = deque([start_node])
    visited = set([start_node])

    while queue:
        curr_node = queue.popleft()

        for next_node in graph[curr_node]:
            if next_node not in visited:
                visited.add(next_node)
                queue.append(next_node)
               
    return visited

N,M = map(int,input().split())
graph = {n+1:[] for n in range(N)}
result = 0
visited = set()
for _ in range(M):
    a,b = map(int,input().split())
    graph[a].append(b)
    graph[b].append(a)

for i in range(N):
    if i+1 not in visited:
        visited.update(bfs(i+1,graph))
        result += 1

print(result)