1 #include<cstdio>
  2 #include<iostream>
  3 #include<cstring>
  4 #include<algorithm>
  5 #include<stack>
  6 #include<vector>
  7 using namespace std;
  8 const int maxn=5010;
  9 const int maxm=500010;
 10 int n,m;
 11 struct edge
 12 {
 13     int u,v,next;
 14 }e[maxm],ee[maxm];
 15 int head[maxn],js,headd[maxn],jss;
 16 int dfsn[maxn],low[maxn],visx,sshu;
 17 int belong[maxn],ss[maxn];
 18 stack<int>st;
 19 bool ins[maxn];
 20 int chudu[maxn];
 21 vector<int>bl[maxn];
 22 vector<int>ans;
 23 void init()
 24 {
 25     memset(head,0,sizeof(head));
 26     memset(e,0,sizeof(e));
 27     js=0;
 28     memset(headd,0,sizeof(headd));
 29     memset(ee,0,sizeof(ee));
 30     jss=0;
 31     memset(dfsn,0,sizeof(dfsn));
 32     memset(low,0,sizeof(low));
 33     visx=sshu=0;
 34     memset(belong,0,sizeof(belong));
 35     memset(ss,0,sizeof(ss));
 36     while(!st.empty())st.pop();
 37     memset(ins,0,sizeof(ins));
 38     memset(chudu,0,sizeof(chudu));
 39     ans.resize(0);
 40     for(int i=0;i<maxn;i++)bl[i].resize(0);
 41 }
 42 void addage(int u,int v,edge e[],int head[],int &js)
 43 {
 44     e[++js].u=u;e[js].v=v;
 45     e[js].next=head[u];head[u]=js;
 46 }
 47 void tarjan(int u)
 48 {
 49     low[u]=dfsn[u]=++visx;
 50     st.push(u);
 51     ins[u]=1;
 52     for(int i=head[u];i;i=e[i].next)
 53     {
 54         int v=e[i].v;
 55         if(dfsn[v]==0)
 56         {
 57             tarjan(v);
 58             low[u]=min(low[u],low[v]);
 59         }
 60         else if(ins[v] && low[u]>dfsn[v]) low[u]=dfsn[v];
 61     }
 62     if(low[u]==dfsn[u])
 63     {
 64         sshu++;
 65         int tp;
 66         do{
 67             tp=st.top();
 68             st.pop();
 69             ins[tp]=0;
 70             bl[sshu].push_back(tp);
 71             belong[tp]=sshu;
 72             ss[sshu]++;
 73         }while(tp!=u);
 74     }
 75 }
 76 void addd(int x)
 77 {
 78     for(int i=0;i<bl[x].size();i++)
 79     {
 80         int y=bl[x][i];
 81         ans.push_back(y);
 82     }
 83 }
 84 
 85 int main()
 86 {
 87     while(scanf("%d%d",&n,&m)==2)
 88     {
 89         init();
 90         for(int u,v,i=0;i<m;i++)
 91         {
 92             scanf("%d%d",&u,&v);
 93             addage(u,v,e,head,js);
 94         }
 95         for(int i=1;i<=n;i++)
 96             if(dfsn[i]==0)tarjan(i);
 97         for(int i=1;i<=m;i++)
 98         {
 99             int u=e[i].u,v=e[i].v;
100             if(belong[u]!=belong[v])
101             {
102                 addage(belong[u],belong[v],ee,headd,jss);
103                 chudu[belong[u]]++;
104             }
105         }
106         for(int i=1;i<=sshu;i++)
107             if(chudu[i]==0)addd(i);
108         sort(ans.begin(),ans.end());
109         for(int i=0;i<ans.size();i++)printf("%d ",ans[i]);
110         printf("\n");
111     }
112     
113     return 0;
114 }