#pragma comment(linker, "/STACK:1024000000,1024000000")

 #include <iostream>

 #include <cstring>

 #include <cstdio>

 #include <queue>

 #include <cstdlib>

 using namespace std;

 #define N 200001

 #define M 2000001

 #define INF 0x3f3f3f3f

 struct node

 {

     int u,v,next;

 }edge[M];

 struct na

 {

     int u,v,w,next;

 }tree[M];

 int first[N],DFN[N],Belong[N],stack[N],Low[N],cnum[N];

 int in[N],d[N],fr[N];

 int qu[M],qv[M];

 int n,m;

 bool vis[M];

 int tot,scnt,top;

 void CL()

 {

     tot = scnt = top = ;

     memset(first,-,sizeof(first));

     memset(fr,-,sizeof(fr));

     memset(in,,sizeof(in));

     memset(DFN,,sizeof(DFN));

     memset(vis,,sizeof(vis));

 }

 void add(int u,int v)

 {

     edge[tot].u = u;

     edge[tot].v = v;

     edge[tot].next = first[u];

     first[u] = tot ++;

 }

 void addt(int u,int v)

 {

     tree[tot].u = u;

     tree[tot].v = v;

     tree[tot].w = ;

     tree[tot].next = fr[u];

     fr[u] = tot ++;

 }

 void Tarjan(int u,int num)

 {

     int v,i;

     DFN[u] = Low[u] = ++ tot;

     stack[top++] = u;

     in[u] = ;

     for(i = first[u];i != -;i = edge[i].next)

     {

         v = edge[i].v;

         if(vis[i]) continue;

         vis[i] = vis[i^] = ;

         if(!DFN[v])

         {

             //printf("cc%d %d",v,i);

             Tarjan(v,i);

             Low[u] = min(Low[u],Low[v]);

         }

         else if(in[v])

         {

             Low[u] = min(Low[u],DFN[v]);

         }

     }

     if(DFN[u] == Low[u])

     {

         scnt ++;

         do

         {

             v = stack[--top];

             Belong[v] = scnt;

             in[v] = ;

             cnum[scnt] ++;

         }while(u != v);

     }

 }

 int spfa(int x)

 {

     int i,key,v,u,minz = ;

     for(i = ;i <= scnt;i ++)

     {

         in[i] = ;

         d[i] = INF;

     }

     queue<int> que;

     in[x] = ;

     d[x] = ;

     que.push(x);

     while(!que.empty())

     {

         u = que.front();

         in[u] = ;

         que.pop();

         for(i = fr[u];i != -;i = tree[i].next)

         {

             v = tree[i].v;

             if(d[v] > d[u] + tree[i].w)

             {

                 d[v] = d[u] + tree[i].w;

                 if(!in[v])

                 {

                     in[v] = ;

                     que.push(v);

                 }

             }

         }

     }

     for(i = ;i <= scnt;i ++)

     {

         if(minz < d[i])

         {

             minz = d[i];

             key = i;

         }

     }

     return key;

 }

 int main()

 {

     int i,u,v,str,x;

     while(scanf("%d%d",&n,&m)!=EOF)

     {

         if(n == &&m == ) break;

         CL();

         for(i = ;i <= m;i ++)

         {

             scanf("%d%d",&u,&v);

             if(i == )

             str = u;

             qu[i] = u;

             qv[i] = v;

             add(u,v);

             add(v,u);

         }

         tot = ;

         Tarjan(u,);

         tot = ;

         for(i = ;i <= m;i ++)

         {

             if(Belong[qu[i]] != Belong[qv[i]])

             {

                 addt(Belong[qu[i]],Belong[qv[i]]);

                 addt(Belong[qv[i]],Belong[qu[i]]);

             }

         }

         if(scnt == )

         printf("0\n");

         else

         {

             x = spfa(spfa());

             printf("%d\n",scnt-d[x]-);

         }

     }

     return ;

 }