program cleaning;

var

  a,b:array[..]of longint;

  n,i,m,j,k,t,g,p:longint;

procedure qsort(l,h:longint);

var i,j,t,m:longint;

begin i:=l; j:=h;

 m:=a[(i+j) div ];

 repeat

 while a[i]<m do inc(i);

 while m<a[j] do dec(j);

 if i<=j then

   begin   t:=a[i]; a[i]:=a[j]; a[j]:=t;   t:=b[i]; b[i]:=b[j]; b[j]:=t;

 inc(i); dec(j);  end;  until i>j;

 if i<h then qsort(i,h); if j>l then qsort(l,j);  end;

begin

  assign(input,'cleaning.in');

  reset(input);

  assign(output,'cleaning.out');

  rewrite(output);

  readln(n,t);

  for i:= to n do

   read(a[i],b[i]);

  qsort(,n);

  k:=;

  for i:= to n do

   begin

    if a[i]<=k then if (b[i]>m)and(b[i]>=p) then m:=b[i];

    if a[i]>k then if a[i]>m+ then begin writeln(-); break; end else  begin k:=m+;p:=k; j:=j+; if m>=t then begin g:=; break; end; m:=b[i];end;

   end;

  if m>=t then if g= then writeln(j+) else writeln(j) else if i=n then writeln(-);

  close(input); close(output);

end.