#include <bits/stdc++.h>
using namespace std;

using std::cin;
using std::cout;

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
bool chmax(T &a, const T b) {if(a<b) {a=b; return true;} else {return false;}}
template<typename T>
bool chmin(T &a, const T b) {if(a>b) {a=b; return true;} else {return false;}}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

vector<int> dijkstra(vector<vector<pair<int, int>>> &graph, int start) {
    int n = (int)graph.size();
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    vector<int> dist(n, INF);
    dist[start] = 0;
    pq.emplace(dist[start], start);
    while(!pq.empty()) {
        pair<int, int> p = pq.top();
        pq.pop();
        int v = p.second;
        if(dist[v] < p.first) continue;
        for(auto e : graph[v]) {
            if(dist[e.first] > dist[v] + e.second) {
                dist[e.first] = dist[v] + e.second;
                pq.emplace(dist[e.first], e.first);
            }
        }
    }
    return dist;
}

void solve() {
    int n, m, k;
    cin >> n >> m >> k;
    vi c(m);
    FOR(m) cin >> c[i];
    vector<vpii> g(n * (k + 1));
    FOR(m) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        rep(j, k + 1) {
            g[u + j*n].emplace_back(v + j*n, c[i]);
            g[v + j*n].emplace_back(u + j*n, c[i]);
            if (j != k) {
                g[u + j*n].emplace_back(v + (j+1)*n, 0);
                g[v + j*n].emplace_back(u + (j+1)*n, 0);
            }
        }
    }
    vi dist = dijkstra(g, 0);
    int ans = INF;
    rep(i, k+1) chmin(ans, dist[n - 1 + i * n]);
    cout << (ans == INF? -1 : ans) << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}