#include<bits/stdc++.h>
using namespace std;
int n,ans = 0;
string a[32][32];
int lx[4]={0,1,0,-1};
int ly[4]={1,0,-1,0};
void SB(int x,int y)
{
    a[x][y] = '-1';
    for(int i = 0; i < 4;i++)
    {
        int tx = x + lx[i];
        int ty = y + ly[i];
        if(tx >= 1 && tx <= n && ty >= 1 && ty <= n && a[tx][ty] == "0")
        {
            SB(tx,ty);
        }
    }
}
int main(){
    cin >> n;
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n;j++)
        {
            cin >> a[i][j];
        }
    }
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1;j <= n; j++)
        {
            if((i == 1||i == n||j == 1 || j == n) && a[i][j] == "0")
            {
                SB(i,j);
            }
        }
    }
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1;j <= n; j++)
        {
        	if(a[i][j] == "0")
        	{
        		ans++;
			}
        }
    }
    cout << ans;
    return 0;
}
/**************************************************************
	Problem: 1913
	User: yangwanning
	Language: C++
	Result: Runtime Error
****************************************************************/