import sys
sys.setrecursionlimit(10 ** 8)

N,M = map(int,input().split())
edge = []
for _ in range(M):
    u,v = map(int,input().split())
    edge.append((u-1,v-1))

parent = [-1] * N
def find(i):
    if parent[i] < 0:
        return i
    parent[i] = find(parent[i])
    return parent[i]
def unite(i,j):
    I = find(i)
    J = find(j)
    if I == J:
        parent[I] -= 1
        return False
    t = min(parent[I],parent[J])
    parent[I] = J
    parent[i] = J
    parent[J] = t - 1
    return True
def isSame(i,j):
    return find(i) == find(j)

ans = 0

for u,v in reversed(edge):
    unite(u,v)
ans = min(parent)
print(-ans - 1)