1 #include <bits/stdc++.h>
 2 using namespace std;
 3
 4 const int maxn = 15;
 5 int nu, nv;
 6 int G[maxn][maxn];
 7 int linker[maxn];
 8 bool vis[maxn];
 9
10 bool dfs(int u) {
11     for(int v = 1; v <= nv; v++) {
12         if(G[u][v] && !vis[v]) {
13             vis[v] = 1;
14             if(linker[v] == -1 || dfs(linker[v])) {
15                 linker[v] = u;
16                 return 1;
17             }
18         }
19     }
20     return 0;
21 }
22
23 int hungary() {
24     int ret = 0;
25     memset(linker, -1, sizeof(linker));
26     for(int u = 1; u <= nu; u++) {
27         memset(vis, 0, sizeof(vis));
28         if(dfs(u)) ret++;
29     }
30     return ret;
31 }
32
33 int n, m;
34 int a[maxn];
35 bool sb[maxn][maxn];
36
37 int main() {
38     // freopen("in", "r", stdin);
39     int x, y;
40     while(~scanf("%d%d",&n,&m)) {
41         nu = nv = n;
42         memset(sb, 0, sizeof(sb));
43         for(int i = 1; i <= n; i++) a[i] = i;
44         a[n+1] = 1;
45         for(int i = 0; i < m; i++) {
46             scanf("%d %d", &x, &y);
47             sb[x][y] = 1;
48         }
49         if(n == 0) {
50             printf("0\n");
51             continue;
52         }
53         int ret = maxn;
54         do {
55             memset(G, 0, sizeof(G));
56             for(int i = 1; i <= n; i++) {
57                 for(int j = 1; j <= n; j++) {
58                     if(!sb[i][a[j]] && !sb[i][a[j+1]]) {
59                         G[i][j] = 1;
60                     }
61                 }
62             }
63             ret = min(ret, n-hungary());
64         }while(next_permutation(a+2, a+n+1));
65         printf("%d\n", ret);
66     }
67     return 0;
68 }