#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 510;
int g[N][N];
bool vis[N][N];
int n;
const int dx[] = {-1,0,1,0};
const int dy[] = {0,1,0,-1};

void bfs(int x,int y){
	queue<pair<int,int>> q;
	q.push({x,y});
	vis[x][y] = true;
	
	while(!q.empty()){
		auto it = q.front();
		q.pop();
		int xx = it.first,yy = it.second;
		
		for(int i=0;i<4;i++){
			int nx = xx + dx[i],ny = yy + dy[i];
			if(nx>=1&&nx<=n&&ny>=1&&ny<=n){
				if(!vis[nx][ny]&&g[nx][ny]==1){
					vis[nx][ny] = true;
					q.push({nx,ny});
				}
			}
		}
	}
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

	cin>>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin>>g[i][j];
		}
	}
    int res=0;
    for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			if(!vis[i][j]&&g[i][j]==1){
				bfs(i,j);
				res++;
			}
		}
	}
    cout<<res;
    return 0;
}