#include <bits/stdc++.h>
using namespace std;
using ll = long long;

template<typename T, bool isMin> struct ConvexHullTrick {
 private:
  deque<pair<T, T>> H;
  inline int sgn(T x) { return x == 0 ? 0 : (x < 0 ? -1 : 1); }
  inline bool check(const pair<T, T> &a, const pair<T, T> &b, const pair<T, T> &c) {
    if(b.second == a.second || c.second == b.second) { return sgn(b.first - a.first) * sgn(c.second - b.second) >= sgn(c.first - b.first) * sgn(b.second - a.second); }
    if(is_integral<T>::value) { return (b.second - a.second) / (a.first - b.first) >= (c.second - b.second) / (b.first - c.first); }
    else { return (b.first - a.first) * sgn(c.second - b.second) / abs(b.second - a.second) >= (c.first - b.first) * sgn(b.second - a.second) / abs(c.second - b.second); }
  }
  inline T get_y(const pair<T, T> &a, const T &x) { return a.first * x + a.second; }

 public:
  ConvexHullTrick() = default;
  bool empty() const { return H.empty(); }
  void clear() { H.clear(); }
  void add(T a, T b) {  // O(n) in total
    if(!isMin) { a *= -1, b *= -1; }
    pair<T, T> line(a, b);
    if(empty()) {
      H.emplace_front(line);
      return;
    }
    if(H.front().first <= a) {
      if(H.front().first == a) {
        if(H.front().second <= b) { return; }
        H.pop_front();
      }
      while(H.size() >= 2 && check(line, H.front(), H[1])) { H.pop_front(); }
      H.emplace_front(line);
    }
    else {
      assert(a <= H.back().first);
      if(H.back().first == a) {
        if(H.back().second <= b) { return; }
        H.pop_back();
      }
      while(H.size() >= 2 && check(H[H.size() - 2], H.back(), line)) { H.pop_back(); }
      H.emplace_back(line);
    }
  }
  T query(T x) {  // O(log n)
    assert(!empty());
    int l = -1, r = H.size() - 1;
    while(l + 1 < r) {
      int m = (l + r) >> 1;
      get_y(H[m], x) >= get_y(H[m + 1], x) ? l = m : r = m;
    }
    return isMin ? get_y(H[r], x) : -get_y(H[r], x);
  }
  T query_inc(T x) {  // query の x が広義単調増加の場合，全体で O(n+q)
    assert(!empty());
    while(H.size() >= 2 && get_y(H.front(), x) >= get_y(H[1], x)) { H.pop_front(); }
    return isMin ? get_y(H.front(), x) : -get_y(H.front(), x);
  }
  T query_dec(T x) {  // query の x が広義単調減少の場合，全体で O(n+q)
    assert(!empty());
    while(H.size() >= 2 && get_y(H.back(), x) >= get_y(H[H.size() - 2], x)) { H.pop_back(); }
    return isMin ? get_y(H.back(), x) : -get_y(H.back(), x);
  }
};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  ll N, M;
  cin >> N >> M;

  vector<ll> W(N);
  for(auto &i : W) { cin >> i; }

  vector<vector<pair<ll, ll>>> g(N);
  for(ll i = 0, u, v, t; i < M; i++) {
    cin >> u >> v >> t;
    u--, v--;
    g[u].emplace_back(v, t);
    g[v].emplace_back(u, t);
  }

  auto Dijkstra = [&](ll s) {
    auto chmin = [&](auto &a, const auto &b) { return a > b ? (a = b, true) : false; };
    vector<ll> d(N, 1e18);
    d[s] = 0;
    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> q;
    q.emplace(0, s);
    while(!q.empty()) {
      auto [tmp, v] = q.top();
      q.pop();
      if(tmp > d[v]) { continue; }
      for(auto &[nv, c] : g[v]) {
        if(chmin(d[nv], d[v] + c)) { q.emplace(d[nv], nv); }
      }
    }
    return d;
  };

  auto s = Dijkstra(0), t = Dijkstra(N - 1);

  vector<ll> idx(N);
  iota(idx.begin(), idx.end(), 0);
  ranges::sort(idx, [&](auto i, auto j) { return W[i] < W[j]; });

  ConvexHullTrick<ll, true> C;
  for(ll i = 0; i < N; i++) { C.add(W[idx[i]], t[idx[i]]); }

  ll ans = s[N - 1];
  for(ll i = 0; i < N; i++) { ans = min(ans, s[idx[i]] + C.query_inc(W[idx[i]])); }

  cout << ans << "\n";
}