#include <bits/stdc++.h>

#define rep(i, a, b) for(int i = (a); i <= (b); i++)
#define pre(i, a, b) for(int i = (a); i >= (b); i--)
#define Ede(i, u) for(int i = h[u]; i; i = ne[i])
#define go(i, a) for(auto i : a)
//#define int long long
#define LL long long
#define ULL unsigned long long
#define PII pair<int, int>
#define PIL pair<int, long long>
#define PLI pair<long long, int>
#define PLL pair<long long, long long>
#define mp make_pair
#define eb emplace_back
#define opb pop_back
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define sf scanf
#define prf printf
#define el putchar('\n')
#define mms(arr, n) memset(arr, n, sizeof(arr))
#define mmc(arr1, arr2) memcpy(arr1, arr2, sizeof(arr2))
#define Db(x) prf("test(%s): ", x)
const int inf = 0x3f3f3f3f;

template <typename T> inline void rd(T &x){
	x = 0; bool f = true; char ch = getchar();
	while(ch < '0' || ch > '9'){ if(ch == '-') f = false; ch = getchar();}
	while(ch >= '0' && ch <= '9'){ x = (x << 1) + (x << 3) + (ch ^ '0'); ch = getchar();}
	if(!f) x = -x;
}
template <typename T, typename ...Args> inline void rd(T &x, Args &...args){ rd(x); rd(args...);}

using namespace std;

const int N = 3e5 + 10, M = N << 1;
int n, m;
int h[N], e[M], ne[M], idx;
void add(int a, int b){
	e[++idx] = b, ne[idx] = h[a], h[a] = idx;
}
int f[N]; //以i为根的符合条件的毛毛虫截断
void dfs(int u, int fa){
	f[u] = 1;
	int mx = 0;
	int sum = 0;
	Ede(i, u){
		int v = e[i];
		if(v == fa) continue;
		dfs(v, u);
		mx = max(mx, f[v]);
		sum++;
	}
	if(sum) f[u] += mx + sum - 1;
}


int main(){
	/*
	freopen(".in", "r", stdin);
	freopen(".out", "w", stdout);
	*/
	rd(n, m);
	rep(i, 1, m){
		int x, y; rd(x, y);
		add(x, y), add(y, x);
	}
	dfs(1, 0);
	LL sum = 0;
	vector<int> maxa; 
	Ede(i, 1){
		int v = e[i];
		sum++;
		maxa.eb(f[v]);
	}
	sort(maxa.begin(), maxa.end());
	LL ans = 1;
	if(sum >= 2) ans = maxa[sum - 1] + maxa[sum - 2] + 1 + sum - 2;
	else if(sum == 1) ans = maxa[sum - 1] + 1;
	prf("%lld\n", ans);
	return 0;
}