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

#define ALL(x) (x).begin(),(x).end()
#define IO ios::sync_with_stdio(false),cin.tie(nullptr);
#define LB(v, x) (ll)(lower_bound(ALL(v),x)-(v).begin())
#define UQ(v) sort(ALL(v)),(v).erase(unique(ALL(v)),v.end())
#define REP(i, n) for(ll i=0; i<(ll)(n); i++)
#define FOR(i, a, b) for(ll i=(ll)(a); (a)<(b) ? i<(b) : i>(b); i+=((a)<(b) ? 1 : -1))
#define chmax(a, b) ((a)<(b) ? ((a)=(b), 1) : 0)
#define chmin(a, b) ((a)>(b) ? ((a)=(b), 1) : 0)

template<typename T> using rpriority_queue=priority_queue<T,vector<T>,greater<T>>;
using ll=long long; const int INF=1e9+10; const ll INFL=4e18; using ld=long double; using ull=uint64_t;
using VI=vector<int>; using VVI=vector<VI>; using VL=vector<ll>; using VVL=vector<VL>;
using PL=pair<ll,ll>; using VP=vector<PL>; using WG=vector<vector<pair<int,ll>>>;



int main(){
    ll N,M,K; cin>>N>>M>>K;
    VL C(M); REP(i,M) cin>>C[i];
    WG G(N);
    REP(i,M){
        ll u,v; cin>>u>>v; u--,v--;
        G[u].push_back({v,C[i]});
        G[v].push_back({u,C[i]});
    }

    VVL dp(K+1,VL(N,INFL)); dp[0][0]=0;
    rpriority_queue<tuple<ll,ll,ll>> pq; pq.push({0,0,0});

    while(!pq.empty()){
        auto [tmp,c,now]=pq.top(); pq.pop();
        if(tmp>dp[c][now]) continue;
        for(auto [nxt,cost]:G[now]){
            if(c+1<=K&&chmin(dp[c+1][nxt],dp[c][now])) pq.push({dp[c+1][nxt],c+1,nxt});
            if(chmin(dp[c][nxt],dp[c][now]+cost)) pq.push({dp[c][nxt],c,nxt});
        }
    }

    ll ans=INFL;
    REP(i,K+1) chmin(ans,dp[i][N-1]);
    if(ans==INFL) ans=-1;

    cout<<ans<<endl;
}