{$m 65520,0,655360}
const maxn=30000;
type arr=array [1..2] of integer;
var f:array [0..maxn] of integer;
    a:array [0..maxn] of arr;
    n:integer;

procedure init;
  var i:integer;
begin
  readln(n);
  for i:=1 to n do read(a[i,1],a[i,2]);
  a[0,1]:=0; a[0,2]:=0;
  fillchar(f,sizeof(f),0);
end;

procedure qsort(l,r:integer);
  var mid,pl,pr:integer;
      k:arr;
begin
  mid:=(l+r) div 2;
  k:=a[mid];
  pl:=l; pr:=r;
  a[mid]:=a[pl];
  while pl<pr do begin
    while (pl<pr) and (a[pr,1]>=k[1]) do dec(pr);
    a[pl]:=a[pr];
    while (pl<pr) and (a[pl,1]<=k[1]) do inc(pl);
    a[pr]:=a[pl];
  end;
  a[pl]:=k;
  if l<mid-1 then qsort(l,mid-1);
  if mid+1<r then qsort(mid+1,r);
end;

procedure main;
  var i,j:integer;
      max:integer;
begin
  f[0]:=0; f[1]:=1;
  for i:=2 to n do begin
    max:=-1;  f[i]:=-1;
    for j:=1 to i-1 do if f[j]>f[i] then f[i]:=f[j];
    for j:=1 to i do if (a[i,1]-a[j,2]>=1) and (f[j]>max) then max:=f
[j];
    if max+1>f[j] then f[j]:=max+1;
  end;
end;

begin
  init;
  qsort(1,n);
  main;
  writeln(f[n]);
end.