program pj024;

var qp:array[0..20,0..20]of boolean;
    n,m,x,y,ans:word;
    f:text;

procedure ss(x,y:word);
 var i:word;
 begin
  if (x=n)and(y=m) then
   inc(ans);

  if (x>=0)and(x<=n)and(y>=0)and(y<=m)and(not(qp[x,y])) then
   for i:=1 to 2 do
    case i of
     1:ss(x+1,y);
     2:ss(x,y+1);
    end;
 end;
begin
 assign(f,'pj024.in');
 reset(f);
 readln(f,n,m,x,y);
 close(f);

 qp[x,y]:=true;

 if (x+2<=n)and(y+1<=m) then   {P1~P8}
  qp[x+2,y+1]:=true;
 if (x+1<=n)and(y+2<=8) then
  qp[x+1,y+2]:=true;
 if (x-1>=0)and(y+2<=m) then
  qp[x-1,y+2]:=true;
 if (x-2>=0)and(y+1<=m) then
  qp[x-2,y+1]:=true;
 if (x-2>=0)and(y-1<=m) then
  qp[x-2,y-1]:=true;
 if (x-1>=0)and(y-2<=m) then
  qp[x-1,y-2]:=true;
 if (x+1<=n)and(y-2>=0) then
  qp[x+1,y-2]:=true;
 if (x+2<=n)and(y-1>=0) then
  qp[x+2,y-1]:=true;

 ss(0,0);

 assign(f,'pj024.out');
 rewrite(f);
 writeln(f,ans);
 close(f);
end.