#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef pair<long long, int> pli;
typedef pair<int, pair<int, int> > piii;
typedef long long ll;
const int N = 6000086, MOD = 1e9 + 7, INF = 0x3f3f3f3f;
ll res;
int n, m, cnt, w[N];
int e[N], ne[N], h[N], idx, t[N];
ll d[N];
bool st[N];

void add(int a, int b, int c) { e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++; }

int main() {
    int k;
    cin >> n >> m >> k;
    memset(h, -1, sizeof(int) * (n + 10) * 4);
    memset(d, 0x3f, sizeof(ll) * (n + 10) * 4);

    for (int i = 1; i < m + 1; i++) scanf("%d", t + i);
    for (int i = 1; i < m + 1; i++) {
        int a, b;
        scanf("%d%d", &a, &b);
        add(a, b, t[i]), add(b, a, t[i]);
        if (k >= 1) add(a, b + n, 0), add(b, a + n, 0), add(a + n, b + n, t[i]), add(b + n, a + n, t[i]);
        if (k >= 2) add(a + n, b + n * 2, 0), add(b + n, a + n * 2, 0), add(a + n * 2, b + n * 2, t[i]), add(b + n * 2, a + n * 2, t[i]);
        if (k == 3) add(a + n * 2, b + n * 3, 0), add(b + n * 2, a + n * 3, 0), add(a + n * 3, b + n * 3, t[i]), add(b + n * 3, a + n * 3, t[i]);
    }
    priority_queue<pli, vector<pli>, greater<pli> > q;
    d[1] = 0;
    q.push({0, 1});
    while (q.size()) {
        auto u = q.top().second; q.pop();
        if (st[u]) continue;
        st[u] = 1;
        for (int i = h[u]; ~i; i = ne[i]) {
            int j = e[i];
            if (d[j] > d[u] + w[i]) d[j] = d[u] + w[i], q.push({d[j], j});
        }
    }
    res = 1e18;
    for (int i = 0; i <= k; i++) res = min(res, d[n * (i + 1)]);
    printf("%lld\n", res < 1e18 ? res : -1);
    return 0; 
}