def find(x):
    if P[x] == x: return x
    else:
        P[x] = find(P[x]) #経路圧縮
        return P[x]
        # return find(P[x]) #経路圧縮なし

def same(x,y):
    return find(x) == find(y)

def unite(x,y):
    x = find(x)
    y = find(y)
    if x == y: return 0
    if x > y: x,y = y,x
    P[y] = x

def group_count():
    for i in range(HW):
        P[i] = find(i)
    return len(set(P))

H, W = map(int, input().split())
HW = H * W
A = [list(map(int, input().split())) for _ in range(H)]

P = [i for i in range(HW + 1)]

for h in range(H):
    for w in range(W):
        if A[h][w] == 0:
            unite(h * W + w, HW)
            continue
        if 0 < h and A[h][w] == A[h - 1][w]:
            unite(h * W + w, (h - 1) * W + w)
        if 0 < w and A[h][w] == A[h][w - 1]:
            unite(h * W + w, h * W + w - 1)
print(group_count() - 1)