#include <bits/stdc++.h>
#define re 
#define m_p make_pair
#define out(x) cerr << #x << " = " << x << " "
#define outln(x) cerr << #x << " = " << x << endl
using namespace std;

const int N = 400005;
const int B = 330;

inline void Rd(int &res){
	re char c;res=0;
	while(c=getchar(),c<48);
	do res=(res<<3)+(res<<1)+(c^48);
	while(c=getchar(),c>47);
}

int n, m;
int deg[N];
array<int, 3> E[N];
vector<pair<int, int> > G[N];
set<pair<int, int> > S[N];

int ans = -1;

int check(int A, int B) {
	if (A == B) return 0;
	auto it = S[A].lower_bound(make_pair(B, 0));
	if (it != S[A].end() && it -> first == B) return it -> second;
	else return 0;
}

int len = 0;
array<int, 3> lis[N];

void add(int u, int v, int val) {
	lis[++len] = {val, u, v};
}

int work(int idx) {
	int answer = -1;
	sort(lis + 1, lis + len + 1);
	reverse(lis + 1, lis + len + 1);
	int k = min(len, 6);
	for (int i = 1; i <= k; ++i) {
		for (int j = i + 1; j <= k; ++j) {
			int p[5] = {idx, lis[i][1], lis[i][2], lis[j][1], lis[j][2]};
			sort(p, p + 5);
			bool err = 0;
			for (int o = 1; o < 5; ++o) err |= (p[o] == p[o - 1]);
			if (!err) {
				// outln("aa");
				answer = max(answer, lis[i][0] + lis[j][0]);
			}
		}
	}
	return answer;
}

void clear() {
	len = 0;
}

void Small(int idx) {
	int sz = (int)(G[idx].size());
	for (int i = 0; i < sz; ++i) {
		for (int j = i + 1; j < sz; ++j) {
			int u = G[idx][i].first, v = G[idx][j].first;
			int p1 = G[idx][i].second;
			int p2 = G[idx][j].second;
			int p3 = check(u, v);
			if (p3) {
				// out(idx); out(u); out(v); out(p1); out(p2); outln(p3);
				add(u, v, p1 + p2 + p3);
			}
		}
	}
}


void Big(int idx) {
	for (int i = 1; i <= m; ++i) {
		int u = E[i][0], v = E[i][1], w = E[i][2];
		int p1 = check(idx, u);
		int p2 = check(idx, v);
		if (p1 && p2) {
			add(u, v, p1 + p2 + w);
		}
	}
}

int main() {
	Rd(n); Rd(m);
	for (int i = 1; i <= m; ++i) {
		int u, v, w;
		Rd(u); Rd(v); Rd(w);
		E[i] = {u, v, w};
		G[u].emplace_back(v, w);
		G[v].emplace_back(u, w);
		S[u].insert(m_p(v, w));
		S[v].insert(m_p(u, w));
		deg[u] += 1; deg[v] += 1;
	}
	for (int i = 1; i <= n; ++i) {
		if (deg[i] <= B) {
			Small(i);
		} else {
			Big(i);
		}
		ans = max(ans, work(i));
		clear();
	}
	printf("%d\n", ans);
	return 0;
}