#include <iostream>
#include <vector>
#include <queue>
#pragma GCC optimize("Ofast")
#define ll long long
#define eps 1e-7
#define all(x) ((x).begin()),((x).end())
#define usecppio ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
using pii = pair<int, int>;
const ll INF = 987654321987654321;
const int MX = 2625;
struct Edge {
int src, dst, w;
bool operator<(const Edge &p) const {
return w > p.w;
}
};
bool relax(int u, int v, int w, ll dist[])
{
bool flag = 0;
if (dist[v] > dist[u] + w && (dist[u] != INF)) {
flag = true;
dist[v] = dist[u] + w;
}
return flag;
}
int fuel[MX];
ll cost[MX * MX];
vector <Edge> G[MX];
void dijkstra(ll dist[], int start, vector<Edge> graph[])
{
fill(dist,dist+MX*MX,INF);
dist[start*2501+fuel[start]] = 0;
priority_queue<Edge> pq;
pq.push({0, start,0});
while(!pq.empty()) {
Edge x = pq.top();
pq.pop();
//printf("Process edge %lld -> %lld (len=%lld)\n",x.src, x.dst, x.w);
for (auto ed : graph[x.dst]) {
bool flag = false;
int max_j = min(2500, fuel[ed.src]);
for (int j = 1; j <= max_j; j++) {
int fcost = min(fuel[ed.dst], j);
if (relax(ed.src*2501+j, ed.dst*2501+fcost, ed.w * j, dist)) {
//printf("cost [%lld][%lld] relaxed to %lld\n",ed.dst, fcost, cost[ed.dst*2501+fcost]);
flag = true;
}
}
if (flag) pq.push(ed);
}
}
}
int32_t main() {
usecppio
int n, m; cin >> n >> m;
for (int i = 1; i <= n; i++) cin >> fuel[i];
for (int i = 0; i < m; i++) {
int u, v, w; cin >> u >> v >> w;
G[u].push_back({u, v, w});
G[v].push_back({v, u, w});
}
dijkstra(cost, 1, G);
ll ans = INF;
for (int j = 1; j <= 2500; j++) ans = min(ans, cost[n*2501+j]);
cout << ans << '\n';
}
