import sys
sys.setrecursionlimit(1000000)
N,M = map(int,input().split())
T = [[i,1] for i in range(2*N+1)]
def rfind(i):
    if T[i][0]==i:
        return i
    return rfind(T[i][0])
def runion(i,j):
    ri = rfind(i)
    rj = rfind(j)
    if ri==rj:return
    if T[ri][1]>=T[rj][1]:
        T[rj][0] = ri
        T[ri][1] += T[rj][1]
    elif T[ri][1]<T[rj][1]:
        T[ri][0] = rj
        T[rj][1] += T[ri][1]
for _ in range(M):
    a,b = map(int,input().split())
    runion(a,b)
visited = [0]*(2*N+1)
ans = 0
for i in range(1,2*N+1):
    ri = rfind(i)
    if visited[ri]==0:
        ans += T[ri][1]//2
        visited[ri] = 1
print(N-ans)