#include <iostream>

#include <cstdio>

#include <queue>

#define REP(i,a,n) for(int i=a;i<=n;++i)

#define pb push_back

using namespace std;

const int N = 3e5+10;

int n,m,clk,ans,cnt;

int dfn[N],low[N],dep[N],q[N],bcc[N];

vector<int> g[N],gg[N];

void dfs(int x, int fa) {

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

	q[++*q] = x;

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

		if (dfn[y]) low[x]=min(low[x],dfn[y]);

		else {

			dfs(y,x);

			low[x] = min(low[x],low[y]);

		}

	}

	if (low[x]==dfn[x]) {

		++cnt;

		do bcc[q[*q]] = cnt; while (q[(*q)--]!=x);

	}

}

void dfs2(int x, int fa) {

	for (int y:gg[x]) if (y!=fa) {

		dfs2(y,x);

		ans = max(ans, dep[x]+dep[y]+1);

		dep[x] = max(dep[x],dep[y]+1);

	}

}

int main() {

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

	while (m--) {

		int u, v;

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

		g[u].pb(v),g[v].pb(u);

	}

	dfs(1,0);

	REP(i,1,n) for (int j:g[i]) {

		if (bcc[i]!=bcc[j]) {

			gg[bcc[i]].pb(bcc[j]);

		}

	}

	dfs2(1,0);

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

}