var     x,y,l,r,z:int64;

procedure init;
begin

end;

function try(x,y,l,r:int64):int64;
begin
        if l=0 then exit(r);
        if r=0 then exit(l);  z:=y+1;
        if z*l>=x then
        begin
                if z>=x then z:=x-1;
                try:=x+z*r;
        end else try:=y+z*l;
end;

function max(x,y:int64):int64;
begin
        if x>y then exit(x) else exit(y);
end;

procedure work;
begin
        while not eof do
        begin
                readln(x,y,l,r);
                writeln(max(try(x,y,l,r),try(y,x,r,l)));
        end;
end;

begin
assign(input,'bs.in');reset(input);
assign(output,'bs.out');rewrite(output);
        init;
        work;
close(input); close(output);
end.