#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;

ostream& operator<<(ostream& os, const modint& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const dynamic_modint<m>& a) {os << a.val(); return os;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}

template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}

const long long INF = 2002002002002002002;
using S = long long;
S _INF(INF);
S _ZERO(0LL);
using F = long long;
S apply(F f, S x){
	return f + x;
}

template<typename S, typename F>
struct Dijkstra{
	struct Edge{
		int from, to;
		F cost;
		Edge(int from, int to, F cost) : from(from), to(to), cost(cost) {};
	};
	int n, m;
	vector<bool> initialized;
	vector<Edge> E;
	vector<vector<int>> G;
	map<int, vector<S>> dist;
	map<int, vector<int>> idx;
	Dijkstra(int _n) : n(_n), m(0), initialized(n, false), G(n){}
	void add_edge(int from, int to, F cost){
		Edge e(from, to, cost);
		E.push_back(e);
		G[from].emplace_back(m);
		m++;
	}
	void calc(int s){
		initialized[s] = true;
		dist[s] = vector<S>(n, _INF);
		idx[s] = vector<int>(n, -1);
		priority_queue<tuple<S, int, int>, vector<tuple<S, int, int>>, greater<tuple<S, int, int>>> pq;
		pq.emplace(_ZERO, s, -1);
		while(pq.size()){
			auto [dist_from, from, index] = pq.top(); pq.pop();
			if(dist[s][from] <= dist_from) continue;
			dist[s][from] = dist_from;
			idx[s][from] = index;
			for(int index : G[from]){
				int to = E[index].to;
				S dist_to = apply(E[index].cost, dist_from);
				if(dist[s][to] <= dist_to) continue;
				pq.emplace(dist_to, to, index);
			}
		}
	}
	S get_dist(int s, int t){
		if(!initialized[s]) calc(s);
		return dist[s][t];
	}
};

int main(){
	int n, m;
	cin >> n >> m;
	assert(1 <= n && n <= 200000);
	assert(0 <= m && m <= 200000);
	vector<long long> w(n);
	for(int i = 0; i < n; i++) cin >> w[i];
	for(int i = 0; i < n; i++) assert(1 <= w[i] && w[i] <= 1000000000);
	set<pair<int, int>> set_for_assert;
	Dijkstra<long long, long long> graph(2 * n);
	for(int i = 0; i < m; i++){
		int u, v;
		long long t;
		cin >> u >> v >> t;
		if(cin.fail()) assert(false);
		assert(1 <= u && u < v && v <= n);
		assert(1 <= t && t <= 1000000000000);
		if(set_for_assert.find(make_pair(u, v)) != set_for_assert.end()) assert(false);
		set_for_assert.insert(make_pair(u, v));
		u--; v--;
		graph.add_edge(u, v, t);
		graph.add_edge(v, u, t);
		graph.add_edge(n + u, n + v, t);
		graph.add_edge(n + v, n + u, t);
	}
	for(int i = 0; i < n; i++) for(int j = 0; j < n; j++){
		if(i == j) continue;
		graph.add_edge(i, n + j, w[i] * w[j]);
	}
	long long ans1 = graph.get_dist(0, n - 1);
	long long ans2 = graph.get_dist(0, 2 * n - 1);
	cout << min(ans1, ans2) << "\n";
	return 0;
}