#include<stdio.h>
long long int u[200005], v[200005], w[200005];
long long int h[1000006], l, z;
long long int dist[100005][4];
long long int comp_h(long long int a, long long int b)
{
	if (z == 0)
	{
		if (u[h[a]] > u[h[b]])
			return 1;
		else
			return -1;
	}
	else
	{
		if (dist[h[a] / 4][h[a] % 4] > dist[h[b] / 4][h[b] % 4])
			return 1;
		else
			return -1;
	}
}
void swap_h(long long int a, long long int b)
{
	long long int f = h[a];
	h[a] = h[b];
	h[b] = f;
	return;
}
void push(long long int ne)
{
	h[l] = ne;
	long long int p = l++;
	for (; p > 0; p = (p - 1) / 2)
		if (comp_h((p - 1) / 2, p) > 0)
			swap_h((p - 1) / 2, p);
	return;
}
long long int pop()
{
	swap_h(0, --l);
	long long int p = 0;
	for (;;)
	{
		if (2 * p + 2 < l)
		{
			if (comp_h(2 * p + 1, 2 * p + 2) > 0)
			{
				if (comp_h(p, 2 * p + 2) > 0)
					swap_h(p, 2 * p + 2);
				p = 2 * p + 2;
			}
			else
			{
				if (comp_h(p, 2 * p + 1) > 0)
					swap_h(p, 2 * p + 1);
				p = 2 * p + 1;
			}
		}
		else if (2 * p + 1 < l)
		{
			if (comp_h(p, 2 * p + 1) > 0)
				swap_h(p, 2 * p + 1);
			p = 2 * p + 1;
		}
		else
			break;
	}
	return h[l];
}
long long int c[200005];
long long int used[100005][4];
int main()
{
	long long int n, m, k;
	scanf("%lld %lld %lld", &n, &m, &k);
	long long int i, j, kk;
	for (i = 0; i < m; i++)
		scanf("%lld", &w[i]);
	for (i = 0; i < m; i++)
	{
		scanf("%lld %lld", &u[i], &v[i]);
		u[i + m] = --v[i];
		v[i + m] = --u[i];
		w[i + m] = w[i];
	}
	m *= 2;
	z = 0;
	l = 0;
	for (i = 0; i < m; i++)
		push(i);
	for (i = 0; i < m; i++)
		c[i] = pop();
	c[m] = m;
	u[m] = -1;
	long long int min, mid, max;
	for (i = 0; i < n; i++)
	{
		dist[i][0] = dist[i][1] = dist[i][2] = dist[i][3] = 1e18;
		used[i][0] = used[i][1] = used[i][2] = used[i][3] = 0;
	}
	dist[0][k] = 0;
	z = 1;
	l = 0;
	push(k);
	while (l > 0)
	{
		i = pop();
		kk = i % 4;
		i /= 4;
		if (used[i][kk] > 0)
			continue;
		used[i][kk]++;
		min = -1;
		max = m;
		while (max - min > 1)
		{
			mid = (max + min) / 2;
			if (u[c[mid]] < i)
				min = mid;
			else
				max = mid;
		}
		for (; u[c[max]] == i; max++)
		{
			j = v[c[max]];
			if (dist[j][kk] > dist[i][kk] + w[c[max]])
			{
				dist[j][kk] = dist[i][kk] + w[c[max]];
				push(4 * j + kk);
			}
			if (kk > 0)
			{
				if (dist[j][kk-1] > dist[i][kk])
				{
					dist[j][kk - 1] = dist[i][kk];
					push(4 * j + kk - 1);
				}
			}
		}
	}
	long long int ans = 1e18;
	for (i = 0; i <= k; i++)
		if (ans > dist[n - 1][i])
			ans = dist[n - 1][i];
	if (ans > 1e15)
		ans = -1;
	printf("%lld\n", ans);
	return 0;
}