class UnionFind:
	def __init__(self, n):
		self.n = n
		self.parents = [-1] * n
	
	def find(self, x):
		if self.parents[x] < 0:
			return x
		else:
			self.parents[x] = self.find(self.parents[x])
			return self.parents[x]
	
	def union(self, x, y):
		x = self.find(x)
		y = self.find(y)
		if x == y:
			return
		if self.parents[x] > self.parents[y]:
			x, y = y, x
		self.parents[x] += self.parents[y]
		self.parents[y] = x

n, m = map(int,input().split())
uf = UnionFind(2 * n)
for i in range(m):
	a, b = map(int,input().split())
	a-=1; b-=1
	uf.union(a, b)

ans = n
for i in range(2*n):
	if uf.find(i) == i:
		siz = -uf.parents[i]
		ans -= siz // 2

print(ans)