1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cmath>
 5 #include<algorithm>
 6 #include<cmath>
 7 #include<queue>
 8 #include<vector>
 9 using namespace std;
10 int N,M,ANS;
11 int a[50][50];
12 void gauss(){
13     for(int i=1;i<=N;i++){
14         int tmp=i;
15         while(tmp<=N&&a[tmp][i]==0) tmp++;
16         if(tmp>N) continue;
17         if(tmp!=i){
18             for(int j=1;j<=N+1;j++) swap(a[i][j],a[tmp][j]);
19         }
20         for(int j=1;j<=N;j++){
21             if(j!=i&&a[j][i]==1){
22                 for(int k=1;k<=N+1;k++) a[j][k]^=a[i][k];
23             }
24         }
25     }
26 }
27 int s[50],cnt;
28 void dfs(int x){
29     if(cnt>=ANS) return;
30     if(x==0){
31         ANS=min(ANS,cnt);
32         return;
33     }
34     if(a[x][x]){
35         int num=a[x][N+1];
36         for(int i=x+1;i<=N;i++)
37             if(a[x][i])
38                 num=num^s[i];
39         s[x]=num;
40         if(num==1) cnt++;
41         dfs(x-1);
42         if(num==1) cnt--;
43     }
44     if(!a[x][x]){
45         s[x]=0;
46         dfs(x-1); s[x]=1; cnt++;
47         dfs(x-1); cnt--;
48     }
49 }
50 int main(){
51     //freopen("lights.in","r",stdin);
52     //freopen("lights.out","w",stdout);
53     scanf("%d%d",&N,&M);
54     for(int i=1;i<=N;i++) a[i][i]=1;
55     for(int i=1,u,v;i<=M;i++){
56         scanf("%d%d",&u,&v);
57         a[u][v]=a[v][u]=1;
58     }
59     for(int i=1;i<=N;i++) a[i][N+1]=1;
60     gauss();
61     ANS=1<<28;
62     dfs(N);
63     printf("%d",ANS);
64     return 0;
65 }