{$A+,B-,D+,E+,F-,G-,I+,L+,N-,O-,P-,Q-,R-,S+,T-,V+,X+}
{$M 16384,0,655360}

program NET;

 type CompNet=record
   C1, C2: byte;
 end;

 var
   t: text;
   N, _B, _E: byte;
   K, i, j: integer;
   C, order: array[1..100] of byte;
   R: array[1..100] of CompNet;
   F: array[1..100] of boolean;
   result: boolean;

 procedure Add (n: byte);
 begin
  C[_E]:=n;
  inc (_E);
 end;

 function Pidh (n: byte): byte;
  var
    i: integer;
 begin
  for i:=1 to K do
    if (R[i].C1=n) and (F[R[i].C2]=false) then
     begin
       Pidh:=R[i].C2;
       F[R[i].C2]:=true;
       Exit;
     end;
  Pidh:=0;
 end;

 function Find_Way (start: byte): boolean;
  var
    i, pr: integer;
 begin
  _B:=1;
  _E:=1;
  Add (start);
  F[1]:=true;
  while _B<>_E do
   begin
     pr:=Pidh (_B);
     if pr=0 then Inc (_B)
     else Add (pr);
   end;
  for i:=1 to N do
    if F[i]=false then
     begin
       Find_Way:=false;
       Exit;
     end;
  Find_Way:=true;
 end;

 function Max: byte;
  var
    i, k: integer;
 begin
   k:=1;
   for i:=2 to N do
     if order[k]<order[i] then k:=i;
   max:=k;
 end;

begin
 result:=true;
 Assign (t, 'NET.DAT');
 Reset (t);
 Readln (t, N, K);
 for i:=1 to K do
   Read (t, R[i].C1, R[i].C2);
 Close (t);
 for i:=1 to N do
   for j:=1 to K do
     if (R[j].C1=i) or (R[j].C2=i) then inc (order[i]);
 for i:=1 to N do
  begin
    j:=Max;
    order[j]:=0;
    if Find_Way (j)=true then Break else if i=N then result:=false;
  end;
 Assign (t, 'NET.RES');
 Rewrite (t);
 if result=false then Writeln (t, 0)
 else Writeln (t, j);
 Close (t);
end.