import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


def sub(es):
    d = {}
    ns = {}
    for u,v in es:
        d.setdefault(u, 0)
        d.setdefault(v, 0)
        ns.setdefault(u, set())
        ns.setdefault(v, set())
        d[u] += 1
        d[v] += 1
        ns[u].add(v)
        ns[v].add(u)
    done = set()
    ans = 0
    used = set()
    for u in ns.keys():
        if u in done:
            continue
        q = [u]
        l = []
        ll = 0
        rr = 0
        while q:
            u = q.pop()
            if d[u]==1:
                l.append(u)
            if u<h:
                ll += 1
            else:
                rr += 1
            for v in ns[u]:
                if v in done:
                    continue
                done.add(v)
                q.append(v)
        if not l:
            ans += min(ll,rr)
        else:
            while l:
#                 print(l,d)
#                 breakpoint()
                u = l.pop()
                if d[u]==0:
                    continue
                v = ns[u].pop()
                if d[v]==0:
                    continue
                assert d[v]>0
                if v not in used:
                    used.add(v)
                    ans += 1
                    for u in ns[v]:
                        d[u] -= 1
                        ns[u].discard(v)
                        if d[u]==1:
                            l.append(u)
    return ans
h,w = list(map(int, input().split()))
d = {}
for i in range(h):
    l = list(map(int, input().split()))
    for j in range(w):
        v = l[j]
        if v==0:
            continue
        d.setdefault(v, [])
        d[v].append((i,j+h))
ans = 0
for k,es in d.items():
    v = sub(es)
    ans += v
#     print(es,v)
print(ans)