#include <bits/stdc++.h>
using namespace std;

int in_range( int h, int w, int x, int y ){
  return 0 <= x and x < h and 0 <= y and y < w;
}

signed main(){
  int H, W; cin >> H >> W;
  int Sx, Sy, Gx, Gy; cin >> Sx >> Sy >> Gx >> Gy; --Sx, --Sy, --Gx, --Gy;
  vector< string > G( H );
  for( int i = 0; i < H; ++i )
    cin >> G[ i ];
  vector< vector< int > > vis( H, vector< int >( W ) );
  queue< pair< int, int > > que;
  que.emplace( Sx, Sy );
  vis[ Sx ][ Sy ] = 1;
  while( not que.empty() ){
    int x, y; tie( x, y ) = que.front(); que.pop();
    if( tie( x, y ) == tie( Gx, Gy ) )
      cout << "YES" << endl, exit( 0 );
    static const int dx[] = { 0, 1, 0, -1 };
    static const int dy[] = { 1, 0, -1, 0 };
    for( int di = 0; di < 4; ++di ){
      int nx = x + dx[ di ], ny = y + dy[ di ];
      if( not in_range( H, W, nx, ny ) ) continue;
      if( not vis[ nx ][ ny ] and abs( G[ nx ][ ny ] - G[ x ][ y ] ) <= 1 )
        vis[ nx ][ ny ] = 1, que.emplace( nx, ny );
      nx += dx[ di ], ny += dy[ di ];
      if( not in_range( H, W, nx, ny ) ) continue;
      if( not vis[ nx ][ ny ] and G[ nx ][ ny ] == G[ x ][ y ] )
        vis[ nx ][ ny ] = 1, que.emplace( nx, ny );
    }
  }
  cout << "NO" << endl;
  return 0;
}