program mengyalan;
const
  maxn=100000;
var
  i,j:longint;
  fi,fo:text;
  axis:array[1..maxn] of integer;
  k:array[1..10000] of boolean;
  c1,c2:longint;
  n,m,sum:integer;
begin
  assign(fi,'punch.in');
  assign(fo,'punch.out');
  reset(fi);
  rewrite(fo);
  readln(fi,n);
  fillchar(k,sizeof(k),false);
  fillchar(axis,sizeof(axis),0);
  m:=0; sum:=0;
  for i:=1 to n do begin
   readln(fi,c1,c2);
   if c2>m then m:=c2;
   for j:=c1 to c2 do axis[j]:=i;
  end;
  for i:=1 to m do
   if (axis[i]>0)and(not(k[axis[i]])) then
    k[axis[i]]:=true;
  for i:=1 to n do if k[i] then inc(sum);
  write(fo,sum);
  close(fi);
  close(fo);
end.