from collections import deque

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))

def BFS(V):
    Q=deque([V[0]])
    S={v:False for v in V}
    S[V[0]]=True
    T=[V[0]]
    U=set(V)
    
    while Q:
        v=Q.popleft()

        N=[]
        if v+1 in U and not S[v+1]:
            Q.append(v+1)
            T.append(v+1)
            S[v+1]=True
            
        if v-1 in U  and not S[v-1]:
            Q.append(v-1)
            T.append(v-1)
            S[v-1]=True
            
        if v+(W+2) in U  and not S[v+(W+2)]:
            Q.append(v+(W+2))
            T.append(v+(W+2))
            S[v+(W+2)]=True
            
        if v-(W+2) in U  and not S[v-(W+2)]:
            Q.append(v-(W+2))
            T.append(v-(W+2))
            S[v-(W+2)]=True

    return T

V=set()
for y in range(H):
    A=list(map(int,input().split()))
    for x in range(W):
        if A[x]==1:
            V.add(f(x+1,y+1))

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

print(k)