program cojs1682;
var
  a,b,i,j,k,m,n,ans:longint;
  z,x:array[1..10000000] of longint;
begin
  assign(input,'ha14d.in');
  assign(output,'ha14d.out');
  reset(input);
  rewrite(output);

  readln(n,m);
  for i:=1 to m do
    begin
      readln(a,b);
      for j:=a to b do
        z[j]:=i;
    end;
  for i:=1 to n do
    if z[i]<>0 then x[z[i]]:=1;
  k:=0;
  for i:=1 to m do
    if x[i]<>0 then inc(ans);
  writeln(ans);

  close(input);
  close(output);
end.