#include<bits/stdc++.h>

#define ll long long

using namespace std;

#define pb push_back

const int N=300005;

vector<int> g[N];

int dfn[N],low[N],num=1,hd[N],n,m,ans=0,v[N];

int to[N*2],ne[N*2],cnt,col[N],mx[N],dc;

bool ban[N*2];

inline void add(int x,int y){ to[++num]=y,ne[num]=hd[x],hd[x]=num;}

void tarjan(int x,int fa){

	dfn[x]=low[x]=++dc;

	for(int i=hd[x];i;i=ne[i]) if(to[i]!=fa)

	    if(!dfn[to[i]]){

	    	tarjan(to[i],x);

	    	low[x]=min(low[x],low[to[i]]);

	    	if(low[to[i]]>dfn[x]) ban[i]=ban[i^1]=1;

		}

		else low[x]=min(low[x],dfn[to[i]]);

}

void B(int x){

	col[x]=cnt;

	for(int i=hd[x];i;i=ne[i])

	    if(ban[i]){

	    	if(col[to[i]]&&v[to[i]]!=cnt){

	    		v[to[i]]=cnt;

	    		g[cnt].pb(col[to[i]]);

	    		g[col[to[i]]].pb(cnt);

			}

		}

		else if(!col[to[i]]) B(to[i]);

}

void dfs(int x,int fa){

	for(int i:g[x]) if(i!=fa){

		dfs(i,x),ans=max(ans,mx[i]+1+mx[x]);

		mx[x]=max(mx[x],mx[i]+1);

	}

}

int main(){

	scanf("%d%d",&n,&m);

	int uu,vv;

	for(int i=1;i<=m;i++){

		scanf("%d%d",&uu,&vv);

		add(uu,vv),add(vv,uu);

	}

	tarjan(1,0);

	for(int i=1;i<=n;i++) if(!col[i]){

		cnt++,B(i);

	}

	dfs(1,0);

	printf("%d\n",ans);

	return 0;

}