#include <bits/stdc++.h>
using namespace std;
using ll=long long;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> int LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> int UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(b<a){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=false){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> void vec_out(vector<T> &p,int ty=0){
    if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
    else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}
template<class T> T square(T a){return a * a;}

using len_type=ll;
struct edge{
    int to;
    len_type length;
};

len_type dijkstra_movement(edge e,int from,len_type t){
    return t+e.length;
}


vector<len_type> dijkstra(vector<vector<edge>> &G,int start,len_type e, len_type inf){
    int M=G.size();
    assert(M>start&&start>=0);
    vector<len_type> seen(M,inf);
    seen[start]=e;
    priority_queue<pair<len_type,int>,vector<pair<len_type,int>>,greater<pair<len_type,int>>> pq;
    pq.push({e,start});
    while(!pq.empty()){
        len_type time;
        int ver;
        tie(time,ver)=pq.top();
        pq.pop();
        if(seen[ver]<time) continue;
        for(edge x:G[ver]){
            len_type T=dijkstra_movement(x,ver,time);
            if(T<seen[x.to]){
                pq.push({T,x.to});
                seen[x.to]=T;
            }
        }
    }
    return seen;
}


void solve();
// CITRUS CURIO CITY / FREDERIC
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N, M, K;
    cin >> N >> M >> K;
    vector<vector<edge>> G(N * (K + 1));
    vector<ll> C(M);
    rep(i, 0, M) cin >> C[i];
    rep(i, 0, M){
        int a, b;
        cin >> a >> b;
        a--, b--;
        rep(rp, 0, 2) {
            swap(a, b);
            rep(j, 0, K) {
                G[a + j * N].push_back({b + (j + 1) * N, 0ll});
            }
            rep(j, 0, K + 1) {
                G[a + j * N].push_back({b + j * N, C[i]});
            }
        }
    }
    auto seen = dijkstra(G, 0, 0, ILL);
    ll ans = ILL;
    // vec_out(seen);
    rep(j, 0, K + 1) chmin(ans, seen[(j + 1) * N - 1]);
    if (ans == ILL) ans = -1;
    cout << ans << "\n";
}