40分请看看，谢谢

var
  n,i,j,k,t,s,r,a,b:longint;
  x,y,c:array[1..100051]of longint;
begin
  read(n,s);
  readln(a,b);
  for i:=1 to n do read(x[i],y[i]);
  for i:=1 to n-1 do begin
    for j:=i+1 to n do begin
      if y[i]>y[j] then begin
        t:=y[i];
        y[i]:=y[j];
        y[j]:=t;
        k:=x[i];
        x[i]:=x[j];
        x[j]:=k;
      end;
    end;
  end;
  k:=1;
  s:=s-y[k];
  t:=1;
  while s>0 do begin
    if x[k]<(a+b) then t:=t+1;
    k:=k+1;
    s:=s-y[k];
  end;
  write(t);
end.