#include<cstdio>

#include<cstring>

#include<queue>

#define rep(i,a,b) for(int i=a;i<=b;++i)

using namespace std;

const int MAXV=;

const int MAXE=;

int DFN[MAXV],low[MAXV],par[MAXV],label[MAXV];

int pointer[MAXV];

int tot,cnt,m,n,Bcnt,ans;

vector<int> graph[MAXV];

int dep[MAXV];

struct Edge

{

    int to,next;

    bool vis;

    Edge() {}

    Edge(int b,int nxt,int flag) {to=b,next=nxt,vis=flag;}

}edge[MAXE];

inline void addedge(int a,int b)

{

    edge[tot]=Edge(b,pointer[a],);

    pointer[a]=tot++;

    edge[tot]=Edge(a,pointer[b],);

    pointer[b]=tot++;

}

void init()

{

    tot=;

    cnt=;Bcnt=;

    memset(pointer,-,sizeof(pointer));

    memset(label,,sizeof(label));

    memset(DFN,,sizeof(DFN));

    rep(i,,n)

    {

        graph[i].clear();

    }

}

void tarjan(int u)

{

    DFN[u]=low[u]=++cnt;

    for(int j=pointer[u];j!=-;j=edge[j].next)

    {

        int v=edge[j].to;

        if(edge[j].vis) continue;

        edge[j].vis=edge[j^].vis=;

        if(!DFN[v])

        {

            par[v]=j;

            tarjan(v);

            if(low[v]<low[u]) low[u]=low[v];

        }

        else if(low[u]>DFN[v]) low[u]=DFN[v];

    }

}

void part(int u)

{

    label[u]=Bcnt;

    for(int j=pointer[u];j!=-;j=edge[j].next)

    {

        int v=edge[j].to;

        if(!label[v]&&edge[j].vis) part(v);

    }

}

void bfs(int s)

{

    rep(i,,Bcnt) dep[i]=-;

    queue<int > q;

    dep[s]=;

    q.push(s);

    while(!q.empty())

    {

        int u=q.front();q.pop();

        for(int j=;j<graph[u].size();++j)

        {

            int v=graph[u][j];

            if(dep[v]==-)

            {

                dep[v]=dep[u]+;

                q.push(v);

            }

        }

    }

}

int diameter()

{

    bfs();

    int ma=,tag;

    rep(i,,Bcnt)

    {

        if(dep[i]>ma)

        {

            tag=i;

            ma=dep[i];

        }

    }

    bfs(tag);

    ma=;

    rep(i,,Bcnt)

    {

        if(dep[i]>ma)

        {

            tag=i;

            ma=dep[i];

        }

    }

    return ma;

}

int main()

{

    //freopen("in.txt","r",stdin);

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

    {

        init();

        int u,v;

        rep(i,,m)

        {

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

            addedge(u,v);

        }

        tarjan();

        int tmp;

        rep(i,,n)

        {

            tmp=par[i]^;

            u=edge[tmp].to;

            if(low[i]>DFN[u])

            {

                edge[tmp].vis=;

                edge[tmp^].vis=;

            }

        }

        Bcnt=;

        rep(i,,n)

        {

            if(!label[i])

            {

                Bcnt++;

                part(i);

            }

        }

        rep(i,,n)

        {

            if(!edge[par[i]].vis)

            {

                tmp=par[i]^;

                u=edge[tmp].to;

                graph[label[u]].push_back(label[i]);

                graph[label[i]].push_back(label[u]);

            }

        }

        printf("%d\n",Bcnt--diameter());

    }

    return ;

}