var i,j,x2,y2,z2,m,n,ans:longint;
    x,y,x1,y1:array[-10..500000] of longint;
    vis,nu,way,num:array[-10..100000] of longint;

procedure init;
begin
    readln(n,m);
  for i:=1 to m do
  begin
    readln(x2,y2);
    x1[i]:=x2;
    y1[i]:=y2;
    inc(way[x2]);inc(nu[x2]);
    inc(way[y2]);inc(nu[y2]);
  end;

  for i:=2 to n do
  way[i]:=way[i-1]+way[i];

  for i:=1 to m do
  begin
    inc(num[x1[i]]);inc(num[y1[i]]);

    x[way[x1[i]-1]+num[x1[i]]]:=x1[i];
    y[way[x1[i]-1]+num[x1[i]]]:=y1[i];
    x[way[y1[i]-1]+num[y1[i]]]:=y1[i];
    y[way[y1[i]-1]+num[y1[i]]]:=x1[i];
 end;
end;

procedure dfs(now:longint);
var i,j:longint;
begin
  vis[now]:=1;

  for i:=way[now-1]+1 to way[now] do
  begin
    dec(nu[y[i]]);
    if (nu[y[i]]<3)and(vis[y[i]]=0) then dfs(y[i]);
  end;

end;

begin
  assign(input,'asm_game.in');
  assign(output,'asm_game.out');
  reset(input);
  rewrite(output);
  init;
  for i:=1 to n do
  if (nu[i]<3)and(vis[i]=0) then dfs(i);

  for j:=1 to n do
  if vis[j]=0 then begin ans:=j;break;end;

  for i:=j+1 to n do
  if vis[i]=0 then ans:=ans xor i;

  writeln(ans);

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