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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, k;
    cin >> n >> m >> k;
    vector<int> c(m);
    for(auto &&v : c) cin >> v;
    vector<vector<pair<int,int>>> g(n);
    for(int i = 0; i < m; i++){
        int u, v;
        cin >> u >> v;
        u--, v--;
        g[u].emplace_back(v, c[i]);
        g[v].emplace_back(u, c[i]);
    }
    priority_queue<pair<ll,int>,vector<pair<ll,int>>,greater<pair<ll,int>>> pq;
    vector<ll> dp(n * (k + 1), 1ll << 60);
    dp[0] = 0;
    pq.emplace(0, 0);
    while(!pq.empty()){
        auto [d, v] = pq.top();
        pq.pop();
        if(d > dp[v]) continue;
        int ofs = v / n * n, fr = v - ofs;
        if(fr == n - 1){
            cout << d << '\n';
            return 0;
        }
        for(auto [u, w] : g[fr]){
            u += ofs;
            if(d + w < dp[u]){
                dp[u] = d + w;
                pq.emplace(dp[u], u);
            }
            if(u + n < dp.size() && d < dp[u + n]){
                dp[u + n] = d;
                pq.emplace(d, u + n);
            }
        }
    }
    cout << "-1\n";
}