from collections import defaultdict, deque
import sys
input = sys.stdin.readline
n, m = map(int, input().split())
graph = defaultdict(list)
def bfs(graph, start, visited):
q = deque()
q.append(start)
visited.add(start)
while q:
node = q.popleft()
child = graph[node]
for c in child:
if c not in visited:
q.append(c)
visited.add(c)
return visited
all_node = set(range(1, n + 1)) # 1부터 n까지 채우기
for i in range(m):
u, v = map(int, input().split())
graph[u].append(v)
graph[v].append(u)
visited = set()
group_cnt = 0
while len(visited) < n:
candidates = all_node - visited # 전체 노드 중 방문하지 않은 노드 집합 구하기
c = candidates.pop() # 집합에서 아무거나 하나 뽑아 쓰기
if c not in visited:
visited = bfs(graph, c, visited)
group_cnt += 1
print(group_cnt)
