var
 i,j,k,l,m,n:longint;
 ans,countO,countX,maxO,maxX,timeO,timeX:int64;
 
function max(a,b:int64):int64;
 begin
  if a>b then exit(a) else exit(b);
 end;
 
procedure work;
 begin
  ans:=max(maxO,maxX);
  if maxX=0 then ans:=max(ans,maxO);
  if maxO=0 then ans:=max(ans,maxX);
  if (maxX=0)or(maxO=0) then exit;
  if countO>=maxO*(countX+1) then ans:=max(ans,countX+(countX+1)*maxO);
  if countX>=maxX*(countO+1) then ans:=max(ans,countO+(countO+1)*maxX);
  if (maxX>=countX)and(maxO>=countO) then ans:=max(ans,countO+countX);
  timeO:=countO div maxO;if countO mod maxO<>0 then timeO:=timeO+1;
  timeX:=countX div maxX;if countX mod maxX<>0 then timeX:=timeX+1;
  if (timeO>=timeX)and(countO<=countX) then ans:=max(ans,countO+countX);
  if (timeX>=timeO)and(countX<=countO) then ans:=max(ans,countO+countX);
  if (timeX>=timeO)and(timeX<=countO) then ans:=max(ans,countO+countX);
  if (timeO>=timeX)and(timeO<=countX) then ans:=max(ans,countO+countX);
  if (countX+1=timeO)or(countO+1=timeX) then ans:=max(ans,countO+countX);
 end;

begin
 assign(input,'bs.in');reset(input);
 assign(output,'bs.out');rewrite(output);
 while not eof do
  begin
   readln(countO,countX,maxO,maxX);
   if countO<maxO then maxO:=countO;
   if countX<maxX then maxX:=countX;
   work;
   writeln(ans);
  end;
 close(input);close(output);
end.