program cch(input,output);
const
 maxs=1000000000;
var
 min,max,n,i,x,y,j,ans:longint;
 flag:array[1..100000] of boolean;
 a:array[0..100000] of integer;

begin
 assign(input,'punch.in');
 assign(output,'punch.out');
 reset(input);
 rewrite(output);
 readln(n);
 min:=maxs; max:=0;
 for i:=1 to n do
  begin
   readln(x,y);
   if x+1<min then min:=x+1;
   if y>max then max:=y;
   for j:=x+1 to y do
    a[j]:=i;
  end;
 for i:=1 to n do flag[i]:=true;
 ans:=0;
 for i:=min  to max do
  if flag[a[i]] then
   begin
    inc(ans);
    flag[a[i]]:=false;
   end;
 write(ans);
 close(input);
 close(output);
end.