char s[199][99];
a,b,x,y;
f(p,q){
	if(!s[p+98][q]++){
		abs(s[p-1][q]-s[p][q])<2&&f(p-1,q);
		abs(s[p+1][q]-s[p][q])<2&&f(p+1,q);
		abs(s[p][q-1]-s[p][q])<2&&f(p,q-1);
		abs(s[p][q+1]-s[p][q])<2&&f(p,q+1);
		s[p-2][q]==s[p][q]&&s[p][q]>s[p-1][q]&&f(p-2,q);
		s[p+2][q]==s[p][q]&&s[p][q]>s[p+1][q]&&f(p+2,q);
		s[p][q-2]==s[p][q]&&s[p][q]>s[p][q-1]&&f(p,q-2);
		s[p][q+2]==s[p][q]&&s[p][q]>s[p][q+1]&&f(p,q+2);
	}
}
main(i){
	scanf("%*d%*d%d%d%d%d ",&a,&b,&x,&y);
	for(;gets(s[++i]+2););
	f(a+1,b+1);
	a=!puts(s[x+99][y+1]?"YES":"NO");
}