from collections import deque
def BFS(V,E):    
    Q=deque([V[0]])
    S={v:False for v in V}
    S[V[0]]=True
    T=[V[0]]

    while Q:
        v=Q.popleft()
        N=[w for w in V if ((v,w) in E) and (not S[w])]

        for w in N:
            Q.append(w)
            T.append(w)
            S[w]=True

    return T

H,W=map(int,input().split())

def f(x,y):
    return y*(W+2)+x

def g(n):
    return (n%(W+2),n//(W+2))

A=[[0]*(W+2)]
for i in range(H):
    A.append([0]+list(map(int,input().split()))+[0])
A+=[[0]*(W+2)]

V=[]
for y in range(H+2):
    for x in range(W+2):
        if A[y][x]==1:
            V.append(f(x,y))

E=set()
for n in V:
    (x,y)=g(n)
    if A[y][x]==1:
        if A[y][x+1]==1:
            E|={(f(x,y),f(x+1,y)),(f(x+1,y),f(x,y))}
        if A[y+1][x]==1:
            E|={(f(x,y),f(x,y+1)),(f(x,y+1),f(x,y))}

U=set()
W=set(V)
k=0
while U!=W:
    k+=1
    U|=set(BFS(list(W-U),E))

print(k)