#include <bitset>
#include <iostream>
#include <unordered_map>
#include <utility>
#include <vector>
constexpr int N = 1E5, M = 1E5;
constexpr int B = 10000;
int u[M], v[M]; int a[M];
std::unordered_map<int, int> a_[N];
std::bitset<B> to[N];
std::vector<int> C[N];
int calc(int w, int i)
{
	return a_[w][u[i]] + a[i] + a_[v[i]][w];
}
bool intersect(int i, int j)
{
	return u[i] == u[j] || u[i] == v[j] || v[i] == u[j] || v[i] == v[j];
}
void chk_max(int& a, int b) { if (a < b) a = b; }
int main()
{
	std::ios_base::sync_with_stdio(false), std::cin.tie(nullptr);
	int n, m; std::cin >> n >> m;
	for (int i = 0; i < m; ++i)
	{
		int& u = ::u[i], & v = ::v[i];
		std::cin >> u >> v >> a[i];
		--u;
		--v;
		a_[u][v] = a_[v][u] = a[i];
	}
	for (int l = 0, r; l < n; l = r)
	{
		r = l + B;
		for (int i = 0; i < n; ++i)
			to[i].reset();
		for (int i = 0; i < m; ++i)
		{
			if (l <= v[i] && v[i] < r)
				to[u[i]].set(v[i] - l);
			if (l <= u[i] && u[i] < r)
				to[v[i]].set(u[i] - l);
		}
		for (int i = 0; i < m; ++i)
		{
			auto&& s = to[u[i]] & to[v[i]];
			for (int j = s._Find_first(); j < B; j = s._Find_next(j))
				C[j].push_back(i);
		}
	}
	int ans = -1;
	for (int i = 0; i < n; ++i)
	{
		auto& C = ::C[i];
		if (C.size() < 2) continue;
		int m = 0;
		for (int j = 0; j < C.size(); ++j)
			if (int s = calc(i, C[j]); s > m)
				m = s, std::swap(C[0], C[j]);
		m = 0;
		for (int j = 1; j < C.size(); ++j)
			if (int s = calc(i, C[j]); s > m)
				m = s, std::swap(C[1], C[j]);
		if (!intersect(C[0], C[1]))
			chk_max(ans, calc(i, C[0]) + calc(i, C[1]));
		else
		{
			int s = calc(i, C[0]);
			for (int j = 2; j < C.size(); ++j)
				if (!intersect(C[0], C[j]))
					chk_max(ans, s + calc(i, C[j]));
			s = calc(i, C[1]);
			for (int j = 2; j < C.size(); ++j)
				if (!intersect(C[1], C[j]))
					chk_max(ans, s + calc(i, C[j]));
		}
	}
	std::cout << ans << "\n";
}