Pascal :

uses math;
var
  i,j,n,t:longint;
	a,h,f,s:array[0..100001]of longint;
function find(l,r:longint):longint;
var mid:longint;
begin
	while l<=r do begin
		mid:=(l+r) shr 1;
		if (a[mid]>h[i])and(a[mid-1]<=h[i]) then exit(mid) else if a[mid]<h[i] then l:=mid+1 else r:=mid-1;
	end;
	exit(l);
end;
procedure qsort(l,r:longint);
var
  i,j,temp,mid:longint;
begin
  i:=l; j:=r;
  mid:=a[(l+r) div 2];
  repeat
    while a[i]<mid do inc(i);
    while a[j]>mid do dec(j);
    if i<=j then
    begin
      temp:=a[i];a[i]:=a[j];a[j]:=temp;
      temp:=h[i];h[i]:=h[j];h[j]:=temp;
      inc(i);dec(j);
    end;
  until i>j;
  if l<j then qsort(l,j);
  if i<r then qsort(i,r);
end;
begin
  readln(n);
	for i:=1 to n do readln(a[i],h[i]);
	qsort(1,n);
	t:=1;
	fillchar(a,sizeof(a),0);
	a[1]:=h[1];
	for i:=2 to n do
		if h[i]>a[t] then begin
			inc(t);
			a[t]:=h[i];
		end
		else a[find(1,t)]:=h[i];
	writeln(t);
end.