import sys
import heapq


def read_input():
    input = sys.stdin.read
    data = input().split()

    index = 0
    N = int(data[index])
    M = int(data[index + 1])
    index += 2
    W = list(map(int, data[index: index + N]))
    index += N
    edges = []
    for _ in range(M):
        U = int(data[index]) - 1
        V = int(data[index + 1]) - 1
        T = int(data[index + 2])
        edges.append((U, V, T))
        index += 3

    return N, M, W, edges


def build_graph(N, edges):
    graph = [[] for _ in range(N)]
    for U, V, T in edges:
        graph[U].append((V, T))
        graph[V].append((U, T))
    return graph


def dijkstra(N, graph, W):
    dist = [float("inf")] * N
    dist[0] = 0
    pq = [(0, 0)]  # (distance, node)

    while pq:
        current_dist, u = heapq.heappop(pq)

        if current_dist > dist[u]:
            continue

        # 航路に沿った移動
        for v, time in graph[u]:
            new_dist = current_dist + time
            if new_dist < dist[v]:
                dist[v] = new_dist
                heapq.heappush(pq, (new_dist, v))

        # ワープ移動
        for v in range(N):
            if v != u:
                warp_time = W[u] * W[v]
                new_dist = current_dist + warp_time
                if new_dist < dist[v]:
                    dist[v] = new_dist
                    heapq.heappush(pq, (new_dist, v))

    return dist[N - 1]


if __name__ == "__main__":
    N, M, W, edges = read_input()
    graph = build_graph(N, edges)
    shortest_time = dijkstra(N, graph, W)
    print(shortest_time)