from sys import stdin, stdout
input = lambda: stdin.readline().rstrip()
write = stdout.write

def main():
    H, W = map(int, input().split())
    A = stdin.read().replace(' ', '').splitlines()

    ans = 0
    for s in A:
        ans += ponds(s)
    if not ans:
        print(0)
        return

    for i in range(H - 1):
        n = int(A[i], 2) & int(A[i+1], 2)
        ans = max(1, ans - ponds(format(n, 'b')))
    print(ans)

def ponds(s):
    s = s.replace('0', ' ')
    cnt = len(s.split())
    return cnt

main()