#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001LL

bool is_p(int n){
	if(n==0)return false;
	if(n == 2) return true;
	if(n == 1 || n % 2 == 0) return false;
	for(int i = 3; i * i <= n; i += 2){
		if(n % i == 0) return false;
	}
	return true;
}

int main(){
	
	vector<vector<int>> dis(45);
	rep(i,900){
		rep(j,45){
			if(is_p(i)&&is_p(i+j)){
				dis[j].push_back(i);
			}
		}
	}
	
	int h,w;
	cin>>h>>w;
	int sx,sy,gx,gy;
	cin>>sx>>sy>>gx>>gy;
	sx--,sy--,gx--,gy--;
	vector<string> s(h);
	rep(i,h)cin>>s[i];
	s[sx][sy] = '.';
	s[gx][gy] = '.';
	vector d(h,vector(w,vector(900,vector<int>(2,Inf32))));
	d[sx][sy][0][0] = 0;
	deque<vector<int>> Q;
	Q.push_back({sx,sy,0,0});
	while(Q.size()>0){
		vector<int> dx = {1,-1,0,0},dy = {0,0,1,-1};
		int x = Q.front()[0],y = Q.front()[1],t = Q.front()[2],k = Q.front()[3];
		Q.pop_front();
		rep(i,4){
			int nx = x+dx[i],ny = y+dy[i];
			if(nx<0||nx>=h||ny<0||ny>=w)continue;
			if(s[nx][ny] == '#')continue;
			int nt = t,nk = k;
			if(i==0)nt++;
			if(i>=2)nk = 1;
			if(nt >= 900)continue;
			int nd = d[x][y][t][k];
			if(i==2)nd++;
			if(nd>=d[nx][ny][nt][nk])continue;
			else{
				d[nx][ny][nt][nk] = nd;
				if(i!=2)Q.push_front({nx,ny,nt,nk});
				else Q.push_back({nx,ny,nt,nk});
			}
		}
		
	}
	int ans = Inf32;
	rep(i,900){
		
		int cur = 0;
		{
			int dd = gx - sx;
			int ii = i;
			if(dd < 0)ii = i-dd;
			dd = abs(dd);
			int tt = distance(dis[dd].begin(),lower_bound(dis[dd].begin(),dis[dd].end(),ii));
			if(tt == dis[dd].size())continue;
			cur += dis[dd][tt] * 2 + dd;
		}
		{
			int dd = gy - sy;
			int ii = d[gx][gy][i][1];
			if(ii==Inf32)continue;
			if(dd < 0)ii = i-dd;
			dd = abs(dd);
			int tt = distance(dis[dd].begin(),lower_bound(dis[dd].begin(),dis[dd].end(),ii));
			if(tt == dis[dd].size())continue;
			cur += dis[dd][tt] * 2 + dd;
		}
		ans = min(ans,cur);
	}
	if(ans == Inf32)cout<<-1<<endl;
	else cout<<ans<<endl;
	return 0;
}