#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 2500
#define M 4000
#define INF 0x3f3f3f3f3f3f3f3fLL
long long min(long long a, long long b) { return a < b ? a : b; }
unsigned int X = 12345;
int rand_() {
return (X *= 3) >> 1;
}
int *ej[N], *ew[N], eo[N];
void append(int i, int j, int w) {
int o = eo[i]++;
if (o >= 2 && (o & o - 1) == 0) {
ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
ew[i] = (int *) realloc(ew[i], o * 2 * sizeof *ew[i]);
}
ej[i][o] = j, ew[i][o] = w;
}
int cc[N];
void sort(int *ii, int l, int r) {
while (l < r) {
int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;
while (j < k)
if (cc[ii[j]] == cc[i_])
j++;
else if (cc[ii[j]] < cc[i_]) {
tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
i++, j++;
} else {
k--;
tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
}
sort(ii, l, i);
l = k;
}
}
long long dd[N], dd_[N];
int iq[N + 1], pq[N], cnt;
int lt(int i, int j) { return dd_[i] < dd_[j]; }
int p2(int p) {
return (p *= 2) > cnt ? 0 : (p < cnt && lt(iq[p + 1], iq[p]) ? p + 1 : p);
}
void pq_up(int i) {
int p, q, j;
for (p = pq[i]; (q = p / 2) && lt(i, j = iq[q]); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_dn(int i) {
int p, q, j;
for (p = pq[i]; (q = p2(p)) && lt(j = iq[q], i); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_add_last(int i) {
iq[pq[i] = ++cnt] = i;
}
int pq_remove_first() {
int i = iq[1], j = iq[cnt--];
if (j != i)
pq[j] = 1, pq_dn(j);
pq[i] = 0;
return i;
}
int main() {
static int ii[N];
int n, m, h, i, j, o, c, w;
long long d;
scanf("%d%d", &n, &m);
for (i = 0; i < n; i++)
scanf("%d", &cc[i]);
for (i = 0; i < n; i++) {
ej[i] = (int *) malloc(2 * sizeof *ej[i]);
ew[i] = (int *) malloc(2 * sizeof *ew[i]);
}
for (h = 0; h < m; h++) {
scanf("%d%d%d", &i, &j, &w), i--, j--;
append(i, j, w), append(j, i, w);
}
for (i = 0; i < n; i++)
ii[i] = i;
sort(ii, 0, n);
memset(dd, 0x3f, n * sizeof *dd);
dd[0] = 0;
for (h = n - 1; h >= 0; h--) {
i = ii[h], c = cc[i];
if (dd[i] == INF)
continue;
memset(dd_, 0x3f, n * sizeof *dd_);
dd_[i] = dd[i], pq_add_last(i);
while (cnt) {
i = pq_remove_first();
dd[i] = min(dd[i], dd_[i]);
for (o = eo[i]; o--; ) {
j = ej[i][o], w = ew[i][o], d = dd_[i] + w * c;
if (dd_[j] > d) {
if (dd_[j] == INF)
pq_add_last(j);
dd_[j] = d, pq_up(j);
}
}
}
}
printf("%lld\n", dd[n - 1]);
return 0;
}
