program cogs1682;
const
 maxn=10000000;
var
l,r,i,j,n,m:longint;
min,max,t,total:longint;
a:array[1..maxn] of longint;
f:array[0..maxn] of boolean;
begin
   assign(input,'ha14d.in'); reset(input);
   assign(output,'ha14d.out'); rewrite(output);
   max:=-maxlongint; min:=maxlongint;   total:=0;
     readln(n,m);
     fillchar(a,sizeof(a),0);
     for i:=1 to m do
      begin
        readln(l,r);
        if r<l then begin t:=l; l:=r; r:=t end;
        if l<min then min:=l;
        if r>max then max:=r;
        for j:=l to r do
            a[j]:=i;
      end;
   for i:=min to max do
     f[a[i]]:=true;
   for i:=1 to m do
     if f[i] then inc(total);
   writeln(total);


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