#include <bits/stdc++.h>
using namespace std;
// #define int long long
using ll=long long;
using vi=vector<int>;
using vl=vector<long long>;
using pii=pair<int,int>;
#define ITR(v,c) for(auto v=begin(c);v!=end(c);v++)
#define FOR(v,a,n) for(int v=a;v<(int)(n);v++)
#define FORE(x,arr) for(auto &x:arr)
#define REP(v,n) FOR(v,0,n)
#define RREP(v,n) for(int v=((int)(n)-1);v>=0;v--)
#define ALL(c) begin(c),end(c)
#define RALL(c) rbegin(c),rend(c)
#define DUMP(x) cerr<<#x<<":="<<(x)<<endl
const int DX[4]={0,1,0,-1}, DY[4]={-1,0,1,0};
const int DX9[9]={0,1,1,1,0,-1,-1,-1,0}, DY9[9]={-1,-1,0,1,1,1,0,-1,0};
const int INF=1e9; const long long INFLL=1e18;
template<class T,class U>ostream&operator<<(ostream &os,const pair<T,U> &p){
    os<<"("<<p.first<<" "<<p.second<<")";return os;}
template<class T>ostream&operator<<(ostream &os,const vector<T> &v){
    ITR(i,v)os<<*i<<(i==end(v)-1?"":" ");return os;}
//------------------------------------------------------------------------------

bool r[51][51];
signed main() {
    int h,w;
    pii s,g;
    cin>>h>>w;
    cin>>s.first>>s.second;
    s.first--; s.second--;
    cin>>g.first>>g.second;
    g.first--; g.second--;
    vector<string> b(h);
    REP(i,h) cin>>b[i];

    queue<pii> q;
    r[s.first][s.second]=true;
    q.push(s);
    while(!q.empty()) {
        pii p=q.front(); q.pop();
        if(p==g) {
            cout<<"YES"<<endl;
            return 0;
        }

        REP(i,4) {
            int nx=p.second+DX[i], ny=p.first+DY[i];
            if(ny<0 || ny>=h || nx<0 || nx>=w) continue;
            if(!r[ny][nx] && b[ny][nx]-b[p.first][p.second]<=1) {
                r[ny][nx]=true;
                q.push(pii(ny,nx));
            }
            nx+=DX[i]; ny+=DY[i];
            if(ny<0 || ny>=h || nx<0 || nx>=w) continue;
            if(!r[ny][nx] && b[ny][nx]==b[p.first][p.second] && b[ny-DY[i]][nx-DX[i]]<b[p.first][p.second]) {
                r[ny][nx]=true;
                q.push(pii(ny,nx));
            }
        }
    }
    cout<<"NO"<<endl;
    return 0;
}