#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

template <class T> std::istream& operator>>(std::istream& is, std::vector<T>& v) {
    for (auto& e : v) {
        is >> e;
    }
    return is;
}

template <class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
    for (std::string_view sep = ""; const auto& e : v) {
        os << std::exchange(sep, " ") << e;
    }
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) {
    return y < x and (x = std::forward<U>(y), true);
}

template <class T, class U = T> bool chmax(T& x, U&& y) {
    return x < y and (x = std::forward<U>(y), true);
}

template <class T> void mkuni(std::vector<T>& v) {
    std::ranges::sort(v);
    auto result = std::ranges::unique(v);
    v.erase(result.begin(), result.end());
}

template <class T> int lwb(const std::vector<T>& v, const T& x) {
    return std::distance(v.begin(), std::ranges::lower_bound(v, x));
}

struct Line {
    mutable long long k, m, p;
    bool operator<(const Line& o) const { return k < o.k; }
    bool operator<(long long x) const { return p < x; }
};

template <bool isMin = true> struct LineContainer : std::multiset<Line, std::less<>> {
    // (for doubles, use inf = 1/.0, div(a,b) = a/b)
    const long long inf = LLONG_MAX / 2;
    long long div(long long a, long long b) {  // floored division
        return a / b - ((a ^ b) < 0 && a % b);
    }
    bool isect(iterator x, iterator y) {
        if (y == end()) {
            x->p = inf;
            return false;
        }
        if (x->k == y->k)
            x->p = x->m > y->m ? inf : -inf;
        else
            x->p = div(y->m - x->m, x->k - y->k);
        return x->p >= y->p;
    }
    void add(long long k, long long m) {
        if (isMin) k = -k, m = -m;
        auto z = insert({k, m, 0}), y = z++, x = y;
        while (isect(y, z)) z = erase(z);
        if (x != begin() && isect(--x, y)) isect(x, y = erase(y));
        while ((y = x) != begin() && (--x)->p >= y->p) isect(x, erase(y));
    }
    long long query(long long x) {
        assert(!empty());
        auto l = *lower_bound(x);
        long long s = 1;
        if (isMin) s = -1;
        return s * (l.k * x + l.m);
    }
};

using ll = long long;

using namespace std;

constexpr ll INF = 4e18;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    int N, M;
    cin >> N >> M;
    vector<ll> W(N);
    cin >> W;
    vector<vector<pair<int, ll>>> G(N);
    for (; M--;) {
        int U, V;
        ll T;
        cin >> U >> V >> T;
        U--, V--;
        G[U].emplace_back(V, T);
        G[V].emplace_back(U, T);
    }

    auto calc = [&](int s) {
        vector<ll> dp(N, INF);
        priority_queue<pair<ll, int>> pq;
        dp[s] = 0;
        pq.emplace(-dp[s], s);
        while (not pq.empty()) {
            auto [val, v] = pq.top();
            pq.pop();
            val *= -1;
            if (dp[v] != val) continue;
            for (auto [u, cost] : G[v]) {
                if (chmin(dp[u], val + cost)) {
                    pq.emplace(-dp[u], u);
                }
            }
        }
        return dp;
    };

    auto f = calc(0), g = calc(N - 1);
    ll ans = f[N - 1];
    LineContainer lc;
    for (int i = 0; i < N; i++) lc.add(W[i], g[i]);
    for (int i = 0; i < N; i++) chmin(ans, f[i] + lc.query(W[i]));

    cout << ans << '\n';
    return 0;
}