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

vector<long long> dijkstra(vector<vector<pair<int,long long>>> &Graph,int start){
int N = Graph.size();
//O((V+E)logV) 一般最短経路魔法.
long long inf = 3e18;
    vector<bool> used(N);
    vector<long long> ret(N,inf);
    priority_queue<pair<long long,int>,vector<pair<long long,int>>,greater<pair<long long,int>>> Q;
    ret.at(start) = 0; Q.push({0,start});
    while(Q.size()){
        auto[nowd,pos] = Q.top(); Q.pop();
        if(used.at(pos)) continue;
        used.at(pos) = true;
        for(auto [to,w] : Graph.at(pos)){
            if(ret.at(to) > nowd+w){
                ret.at(to) = nowd+w;
                Q.push({ret.at(to),to});
            }
        }
    }
    return ret;
}
vector<long long> dijkstra2(vector<vector<pair<int,long long>>> &Graph,int start){
    int N = Graph.size();
    //O(V^2) 密グラフ専用.
    long long inf = 3e18;
    vector<bool> used(N);
    vector<long long> ret(N,inf);
    ret.at(start) = 0;
    while(true){
        long long nowd = inf,pos = -1;
        for(int i=0; i<N; i++){
            if(used.at(i)) continue;
            if(nowd > ret.at(i)) nowd = ret.at(i),pos = i;
        }
        if(pos == -1) break;
        used.at(pos) = true;
 
        for(auto [to,w] : Graph.at(pos)){if(ret.at(to) > nowd+w) ret.at(to) = nowd+w;}
    }
    return ret;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,M,K; cin >> N >> M >> K;
    vector<long long> C(M);
    for(auto &c : C) cin >> c;

    vector<vector<pair<int,long long>>> Graph((K+1)*N);
    for(int i=0; i<M; i++){
        int u,v; cin >> u >> v;
        u--; v--;
        long long w = C.at(i);
        for(int k=0; k<=K; k++){
            Graph.at(N*k+u).push_back({N*k+v,w});
            Graph.at(N*k+v).push_back({N*k+u,w});
            if(k < K){
                Graph.at(N*k+v).push_back({N*k+u+N,0});
                Graph.at(N*k+u).push_back({N*k+v+N,0});
            }
        }
    }

    auto dist = dijkstra(Graph,0);
    long long answer = 1e18;
    for(int i=0; i<=K; i++) answer = min(answer,dist.at(N-1+N*i));
    if(answer > 1e17) answer = -1;
    cout << answer << endl;
}