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  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<algorithm>
  5 #include<queue>
  6 #include<cmath>
  7 #include<vector>
  8 using namespace std;
  9 #define INF 0x3f3f3f3f
 10 const int maxn = 6e4+10;
 11 int n,m,s,t,u,v;
 12 struct Edge {
 13     int from, to, cap, flow;
 14 };
 15 vector<Edge> edges;
 16 vector<int> G[maxn];
 17 bool vis[maxn];
 18 int d[maxn], cur[maxn],nxt[maxn];
 19
 20 void Init()
 21 {
 22     memset(d,0,sizeof d);
 23     for(int i=0;i<=2*n+1;i++) G[i].clear();
 24 }
 25
 26 void AddEdge(int from, int to, int cap)
 27 {
 28     edges.push_back((Edge){from, to, cap, 0});
 29     edges.push_back((Edge){to, from, 0, 0});
 30     int m = edges.size();
 31     G[from].push_back(m-2); G[to].push_back(m-1);
 32 }
 33
 34 bool bfs()
 35 {
 36     memset(vis,0,sizeof vis);
 37     queue<int> q;
 38     q.push(s);
 39     d[s] = 0; vis[s] = 1;
 40     while (!q.empty())
 41     {
 42         int x = q.front(); q.pop();
 43         for(int i = 0; i < G[x].size(); ++i)
 44         {
 45             Edge &e = edges[G[x][i]];
 46             if (!vis[e.to] && e.cap > e.flow)
 47             {
 48                 vis[e.to] = 1;
 49                 d[e.to] = d[x] + 1;
 50                 q.push(e.to);
 51             }
 52         }
 53     }
 54     return vis[t];
 55 }
 56
 57 int dfs(int x,int a)
 58 {
 59     if(x == t || a == 0) return a;
 60     int flow = 0, f;
 61     for(int &i = cur[x]; i < G[x].size(); ++i)
 62     {
 63         Edge &e = edges[G[x][i]];
 64         if (d[e.to] == d[x] + 1 && (f=dfs(e.to, min(a, e.cap-e.flow))) > 0)
 65         {
 66             e.flow += f;
 67             edges[G[x][i]^1].flow -= f;
 68             flow += f; a -= f;
 69             if (a == 0) break;
 70         }
 71     }
 72     return flow;
 73 }
 74
 75 int MaxFlow(int s, int t)
 76 {
 77     int flow = 0;
 78     while (bfs())
 79     {
 80         memset(cur,0,sizeof cur);
 81         flow += dfs(s, INF);
 82     }
 83     return flow;
 84 }
 85
 86 int main()
 87 {
 88     while(scanf("%d%d",&n,&m)!=EOF)
 89     {
 90         Init();
 91         for(int i=1;i<=m;i++)
 92         {
 93             scanf("%d%d",&u,&v);
 94             AddEdge(u,v+n,1);
 95         }
 96         s=0,t=2*n+1;
 97         for(int i=1;i<=n;i++)
 98         {
 99             AddEdge(s,i,1);
100             AddEdge(i+n,t,1);
101         }
102         int ans=MaxFlow(s,t);
103         memset(nxt,0,sizeof nxt);
104         memset(vis,0,sizeof vis);
105
106         for(int i=1;i<=n;i++)
107         {
108             for(int j=0;j<G[i].size();j++)
109             {
110                 Edge &e=edges[G[i][j]];
111                 if(e.flow>0) nxt[e.from]=e.to-n;
112             }
113         }
114         for(int i=1;i<=n;i++)
115         {
116             if(!vis[i])
117             {
118                 int a=i;
119                 vis[a]=1;
120                 printf("%d",a);
121                 while(nxt[a])
122                 {
123                     a=nxt[a];
124                     vis[a]=1;
125                     printf(" %d",a);
126                 }
127                 printf("\n");
128             }
129         }
130         printf("%d\n",n-ans);
131     }
132     return 0;
133 }