var
  x,y:array[1..1000]of longint;
  a:array[1..1000]of boolean;
  n,m,i,j,zong:longint;
begin
  assign(input,'hal4d.in');reset(input);
  assign(output,'hal4d.out');rewrite(output);
  read(n,m);fillchar(a,sizeof(a),true);
  fillchar(x,sizeof(x),0);y:=x;
  for i:=1 to m do
  begin
    read(x[i],y[i]);
    for j:=1 to i-1 do
    if a[j]=true then
    begin
      if (x[j]>=x[i]) and (y[j]<=y[i]) then begin a[j]:=false;break;end;
      if (x[j]>=x[i]) and (x[j]<=y[i]) and (y[j]>y[i]) then x[j]:=y[i]+1;
      if (x[j]<x[i]) and (y[j]>=x[i]) and (y[j]<=y[i]) then y[j]:=x[i]-1;
    end;
  end;
  for i:=1 to m do if a[i]=true then zong:=zong+1;
  writeln(zong);
  close(input);close(output);
end.