class UnionFind:
    def __init__(self, N):
        self.par = [-1] * N
        self.size = [1] * N
    def root(self, x):
        while self.par[x] >= 0:
            x = self.par[x]
        return x
    def union(self, x, y):
        rx = self.root(x)
        ry = self.root(y)
        if rx == ry:
            return
        if self.size[rx] < self.size[ry]:
            rx, ry = ry, rx
        self.par[ry] = rx
        self.size[rx] += self.size[ry]
    
    def find(self, x, y):
        return self.root(x) == self.root(y)

N, M = map(int, input().split())
box = UnionFind(M + 1)
bi = {}
info = [list(map(int, input().split())) for i in range(M)]
for i in range(M):
    b, c = info[i]
    if bi.get(c, 0) == 0:
        bi[c] = b
    else:
        box.union(b, bi[c])
ans = 0
done = [False] * (M + 1)
for i in range(1, M + 1):
    p = box.root(i)
    if not done[p]:
        ans += box.size[p] - 1
print(ans)