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var
  a,next,v,low,dfn,st,be:array[0..5000000]of longint;
  b:array[0..5000000]of boolean;
  n,m,i,j,k,p,q:longint;
procedure adde(uu,vv:longint);
begin
  inc(k);
  v[k]:=vv;
  next[k]:=a[uu];
  a[uu]:=k;
end;
procedure dfs(n:longint);
var
  i:longint;
begin
  inc(k);
  dfn[n]:=k;
  low[n]:=k;
  b[n]:=true;
  inc(st[0]);
  st[st[0]]:=n;
  i:=a[n];
  while i<>0 do
  begin
    if dfn[v[i]]=0 then
    begin
      dfs(v[i]);
      if low[v[i]]<low[n] then low[n]:=low[v[i]];
    end
    else if b[v[i]] and (dfn[v[i]]<low[n]) then low[n]:=dfn[v[i]];
    i:=next[i];
  end;
  if dfn[n]=low[n] then
  begin
    inc(t);
    repeat
      be[st[st[0]]]:=t;
      b[st[st[0]]]:=false;
      dec(st[0]);
    until st[st[0]+1]=n;
  end;
end;
procedure adde2(uu,vv:longint);
begin
  inc(k);
  v2[k]:=vv;
  next2[k]:=a2[uu];
  a2[uu]:=k;
end;
begin
  read(n,m);
  for i:=1 to m do
  begin
    read(p,q);
    adde(p,q);
  end;
  k:=0;
  fillchar(b,sizeof(b),false);
  for i:=1 to n do if be[i]=0 then
  dfs(i);//be[i]表示i属于的强连通分量的编号
end.