#include <bits/stdc++.h>
#include <atcoder/all>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n ,m ,k;
    cin >> n >> m >> k;
    vector<int> c(m);
    rep(i,m) cin >> c[i];
    vector<vector<P>> g(n*(k+1));
    rep(i,m) {
        int u, v;
        cin >> u >> v;
        --u;--v;
        g[u].emplace_back(v, c[i]);
        g[v].emplace_back(u, c[i]);
        for(int j=1;j<=k;j++) {
            g[u+n*(j-1)].emplace_back(v+n*j,0);
            g[v+n*(j-1)].emplace_back(u+n*j,0);
            g[u+n*j].emplace_back(v+n*j,c[i]);
            g[v+n*j].emplace_back(u+n*j,c[i]);
        }
    }   
    priority_queue<P,vector<P>,greater<P>> pq;
    pq.emplace(0,0);
    const ll INF = 1e18;
    vector<ll> dist(n*(k+1),INF);
    dist[0] = 0;
    while(!pq.empty()) {
        auto [d, u] = pq.top();pq.pop();
        if(d!=dist[u]) continue;
        for(auto [v, c] : g[u]) {
            if(dist[v]>dist[u]+c) {
                dist[v] = dist[u] + c;
                pq.emplace(dist[v], v);
            }
        }
    }
    dbg(dist);
    ll ans = INF;
    rep(i,k+1) ans = min(ans, dist[n-1+i*n]);
    if(ans==INF) ans = -1;
    cout << ans << endl;
    return 0;
}