program pj024(f1,f2);
var
  a:array[-3..23,-3..23,1..2]of longint;
  i,j,n,m,c,b:integer;
  ans:longint;
  f1,f2:text;
begin
  assign(f1,'pj024.in'); assign(f2,'pj024.out');
  reset(f1);  rewrite(f2);
  read(f1,n,m,c,b);
  for i:=-3 to 23 do begin
    for j:=-3 to 23do a[i,j,2]:=0;
  end;
  for i:=0 to n do begin
    for j:=0 to m do begin
      a[i,j,2]:=1;
      a[i,j,1]:=0;
    end;
  end;
  a[0,0,1]:=1; a[c,b,2]:=0;
  a[c+2,b+1,2]:=0; a[c-2,b+1,2]:=0;
  a[c+1,b+2,2]:=0; a[c-1,b+2,2]:=0;
  a[c+2,b-1,2]:=0; a[c-2,b-1,2]:=0;
  a[c+1,b-2,2]:=0; a[c-1,b-2,2]:=0;
  for i:=0 to n do begin
    for j:=0 to m do begin
      if a[i+1,j,2]=1 then a[i+1,j,1]:=a[i+1,j,1]+a[i,j,1];
      if a[i,j+1,2]=1 then a[i,j+1,1]:=a[i,j+1,1]+a[i,j,1];
    end;
  end;
  writeln(f2,a[n,m,1]);
  close(f1); close(f2);
end.