program ex;
type
 ss=array[1..100]of integer;
var
 a,h:ss;
 f1,f2:text;
 n,m:integer;
procedure init;
 var
  i:integer;
 begin
  assign(f1,'goblin.in');
  assign(f2,'goblin.out');
  reset(f1);
  rewrite(f2);
  readln(f1,n,m);
  for i:=1 to m do
   readln(f1,a[i],h[i]);
  close(f1);
 end;
function pd:boolean;
 var
  i,t:integer;
 begin
  pd:=true;
  for i:=1 to m do
   if a[i]=h[i] then inc(t);
  if t=i then exit(false);
 end;
begin
 init;
 if pd=false then writeln(f2,'0');
 close(f2);
end.