都说洛谷数据水，vijos深搜过了，这却过不了，只能递推

var
 n,m,c,d,i,j:longint;
 a:array[0..20,0..20] of int64;
 b:array[0..20,0..20] of boolean;
function go(n,m:longint):longint;
begin
 if a[n,m]=0 then exit;
 if a[n,m]<>0 then go:=a[n,m]
  else if (n-1>=0) and (m-1>=0) then go:=go(n-1,m)+go(n,m-1);
end;
procedure jq(x,y:longint);
begin
fillchar(b,sizeof(b),true);
b[x,y]:=false;
if x-2>=0 then begin
if y-1>=0 then b[x-2,y-1]:=false;
if y+1<=m then b[x-2,y+1]:=false;
end;
if x+2<=n then begin
if y-1>=0 then b[x+2,y-1]:=false;
if y+1<=m then b[x+2,y+1]:=false;
end;
if y-2>=0 then begin
if x-1>=0 then b[x-1,y-2]:=false;
if x+1<=n then b[x+1,y-2]:=false;
end;
if y+2<=m then begin
if x-1>=0 then b[x-1,y+2]:=false;
if x+1<=n then b[x+1,y+2]:=false;
end;
end;
begin
 read(n,m,c,d);
 jq(c,d);
 for i:=1 to n do if b[i,0]=false then break else a[i,0]:=1;
 for i:=1 to m do if b[0,i]=false then break else a[0,i]:=1;
 for i:=1 to n do
  for j:=1 to m do
   if b[i,j]<>false then a[i,j]:=a[i-1,j]+a[i,j-1];
 write(a[n,m]);
end.