#include <bits/stdc++.h>
using namespace std;
struct node{
	int x,y,step;
};
queue<node> q;
int dis[4][2]={{1,0},{0,1},{0,-1},{-1,0}},ans;
int n,t;
char a[1005][1005];
int book[1005][1005];
int main()
{
	cin>>n>>t;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			cin>>a[i][j];
	while(t--)
	{
		memset(book,0,sizeof(book));
		int sx,sy;
		cin>>sx>>sy;
		q.push(node{sx,sy,0});
		ans=0;
		while(!q.empty())
		{
			int nx=q.front().x;
			int ny=q.front().y;
			int step1=q.front().step;
			q.pop();
			for(int k=0;k<4;k++)
			{
				int x1=nx+dis[k][0];
				int y1=ny+dis[k][1];
				if(x1>=1&&x1<=n&&y1>=1&&y1<=n&&book[x1][y1]==0&&((a[x1][y1]=='1'&&a[nx][ny]=='0')||(a[x1][y1]=='0'&&a[nx][ny]=='1')))
				{
					book[x1][y1]=1;
					q.push(node{x1,y1,step1+1});
					ans=max(ans,step1+1);
				}
			}	
		}
		cout<<ans<<endl;;
	}
	return 0;
}