program ex(f1,f2);
 type
  zn=array [1..100010] of longint;
  ka=array [0..1000010] of integer;
  la=array [1..100010] of boolean;
 var
  head,tail:zn;
  c:ka; flag:la;
  f1,f2:text;
  i,j,k,p,m,n,l,ans,max:longint;
 begin
  assign(f1,'punch.in'); reset(f1);
  assign(f2,'punch.out'); rewrite(f2);
  readln(f1,n); max:=0; ans:=0;
  for i:=1 to n do flag[i]:=true;
  for i:=1 to n do
   begin
    readln(f1,head[i],tail[i]);
    if tail[i]>max then max:=tail[i];
    for j:=head[i]+1 to tail[i] do
     c[j]:=i;
   end;
  for i:=1 to max do
   if (flag[c[i]])and(c[i]>=1) then
    begin
     inc(ans);
     flag[c[i]]:=false;
    end;
  writeln(f2,ans);
  close(f1);
  close(f2);
 end.