1 #include <iostream>
 2 #include <cstdio>
 3 
 4 using namespace std;
 5 
 6 const int INF=999999;
 7 
 8 int Map[210][210],n;
 9 
10 int settle()
11 {
12     for (int i=0; i<n; i++)
13     {
14         //node[i]=INF;
15         for (int j=0; j<n; j++)
16         {
17             Map[i][j]=INF;
18         }
19     }
20 }
21 
22 int floyd()
23 {
24     for (int k=0; k<n; k++)
25     {
26         for (int i=0; i<n; i++)
27         {
28             for (int j=0; j<n; j++)
29             {
30                 if (Map[i][j]>Map[i][k]+Map[k][j])
31                     Map[i][j]=Map[i][k]+Map[k][j];
32             }
33         }
34     }
35 
36 }
37 
38 int main()
39 {
40     int m;
41     while (~scanf("%d%d",&n,&m))
42     {
43         settle();
44         while (m--)
45         {
46             int a,b;
47             scanf("%d%d",&a,&b);
48             Map[a][b]=Map[b][a]=1;
49         }
50         floyd();
51         int MAx=0;
52         for (int i=0; i<n; i++)
53         {
54             for (int j=0; j<n; j++)
55             {
56                 if (MAx<Map[i][j])
57                     MAx=Map[i][j];
58             }
59         }
60         if (MAx>7)
61             printf ("No\n");
62         else
63             printf ("Yes\n");
64     }
65     return 0;
66 }