#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
#define vv(a,b,c,d) vector<vector<a> >(b,vector<a>(c,d))
#define vvv(a,b,c,d,e) vector<vector<vector<a> > >(b,vv(a,c,d,e))
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

const int D[] = { 0,-1,0,1,0 };

class UnionFind{
    int cnt;
    vector<int> par, rank, size;
public:
    UnionFind(){}
    UnionFind(int _n):cnt(_n), par(_n), rank(_n), size(_n, 1){
        for(int i=0;i<_n;++i) par[i]=i;
    }
    int find(int k){
        return (k==par[k])?k:(par[k]=find(par[k]));
    }
    int operator[](int k){
        return find(k);
    }
    int getSize(int k){
        return size[find(k)];
    }
    void unite(int x, int y){
        x = find(x); y = find(y);
        if(x==y) return;
        --cnt;
        if(rank[x] < rank[y]){
            par[x] = y;
            size[y] += size[x];
        }else{
            par[y] = x;
            size[x] += size[y];
            if(rank[y] == rank[x]) ++rank[x];
        }
    }
    int count(){
        return cnt;
    }
};

bitset<3001> A[3001];

int main() {

    int H, W;
    cin >> H >> W;
    UnionFind uf(H*W + 1);
    auto f = [&](int y, int x) {
        RT y*W + x;
    };
    rep(y, H)rep(x, W) {
        int z;
        scanf("%d", &z);
        A[y][x] = z;
        if (!z)uf.unite(H*W, f(y, x));
    }

    rep(y, H)rep(x, W)if (A[y][x]) {
        if (A[y + 1][x])uf.unite(f(y, x), f(y + 1, x));
        if (A[y][x + 1])uf.unite(f(y, x), f(y, x + 1));
    }

    cout << uf.count() - 1 << endl;
}