1 #include<bits/stdc++.h> 2 #define _for(i,a,b) for(register int i = (a);i < b;i ++) 3 #define _rep(i,a,b) for(register int i = (a);i > b;i --) 4 #define INF 0x3f3f3f3f 5 #define MOD 100000000 6 #define maxn 100003 7 #define pb push_back 8 #define debug() printf("Miku Check OK! ") 9 typedef long long ll; 10 11 using namespace std; 12 typedef pair<int,int> P; 13 inline ll read() 14 { 15 ll ans = 0; 16 char ch = getchar(), last = ' '; 17 while(!isdigit(ch)) last = ch, ch = getchar(); 18 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar(); 19 if(last == '-') ans = -ans; 20 return ans; 21 } 22 inline void write(ll x) 23 { 24 if(x < 0) x = -x, putchar('-'); 25 if(x >= 10) write(x / 10); 26 putchar(x % 10 + '0'); 27 } 28 int ver[maxn],Next[maxn],head[maxn],val[maxn]; 29 int d[maxn]; 30 int n,m,s,t,tot,maxflow; 31 void add(int x,int y,int w) 32 { 33 ver[++tot] = y,Next[tot] = head[x],head[x] = tot,val[tot] = w; 34 } 35 bool bfs() 36 { 37 memset(d,0,sizeof(d)); 38 queue<int> q; 39 q.push(s);d[s] = 1; 40 while(!q.empty()) 41 { 42 int x = q.front();q.pop(); 43 for(int i = head[x]; i; i = Next[i]) 44 if(val[i] && !d[ver[i]]) 45 { 46 q.push(ver[i]); 47 d[ver[i]] = d[x]+1; 48 if(ver[i]==t) 49 return true; 50 } 51 } 52 return false; 53 } 54 int dinic(int x,int flow) 55 { 56 if(x==t) return flow; 57 // k为子节点增量 58 int rest = flow, k; 59 for(int i = head[x]; i && rest; i = Next[i]) 60 { 61 if(val[i] && d[ver[i]] == d[x]+1) 62 { 63 k = dinic(ver[i],min(rest,val[i])); 64 if(!k) d[ver[i]] = 0; 65 val[i] -= k; 66 val[i^1] += k; 67 rest -= k; 68 } 69 } 70 return flow - rest; 71 } 72 vector<int> st; 73 int vvis[maxn]; 74 void go(int i,vector<int>& rnt) 75 { 76 rnt.pb(i); 77 for(int j = head[i]; j ; j = Next[j]) 78 { 79 int y = ver[j]; 80 if(y>n && !vvis[y-n] && !val[j]) 81 { 82 vvis[y-n] = 1; 83 go(y-n,rnt); 84 } 85 } 86 } 87 int main() 88 { 89 n = read();m = read(); 90 tot = 1;maxflow = 0;s = 0;t = 2*n+1; 91 _for(i,1,m+1) 92 { 93 int x = read();int y = read(); 94 add(x,y+n,1);add(y+n,x,0); 95 } 96 _for(i,1,n+1) 97 { 98 add(0,i,1);add(i,0,0); 99 add(i+n,2*n+1,1);add(2*n+1,i+n,0); 100 } 101 int flow = 0; 102 while(bfs()) 103 while(flow = dinic(s,INF)) 104 maxflow += flow; 105 vvis[0] = 1; 106 _for(i,1,n+1) 107 { 108 for(int j = head[i+n]; j ; j = Next[j]) 109 if(ver[j]==2*n+1 && val[j]==1) 110 st.pb(i),vvis[i] = 1; 111 } 112 113 vector<int> tmp; 114 _for(i,0,st.size()) 115 { 116 vvis[st[i]] = 1,go(st[i],tmp); 117 _for(j,0,tmp.size()-1) 118 printf("%d ",tmp[j]); 119 printf("%d ",tmp[tmp.size()-1]); 120 tmp.clear(); 121 } 122 123 write(n-maxflow); 124 return 0; 125 }