from heapq import heappush, heappop

INF = 10 ** 18

def dijkstra(s, N): # (始点, ノード数)
    dist = [INF for _ in range(N)]
    hq = [(0, s)]
    dist[s] = 0
    seen = [0] * N # ノードが確定済みかどうか
    while hq:
        d, v = heappop(hq) # ノードを pop する
        if seen[v]:
            continue
        seen[v] = 1
        for to, cost in G[v]: # ノード v に隣接しているノードに対して
            if dist[v] + cost < dist[to]:
                dist[to] = dist[v] + cost
                heappush(hq, (dist[to], to))
    return dist

import sys
input = sys.stdin.readline
N, M, K = map(int, input().split())
C = list(map(int, input().split()))
G = [[] for _ in range(N*(K+1))]
for i in range(M):
    u, v = map(int, input().split())
    u-=1
    v-=1
    for k in range(K+1):
        G[u+N*k].append((v+N*k, C[i]))
        G[v+N*k].append((u+N*k, C[i]))
    for k in range(K):
        G[u+N*k].append((v+N*(k+1), 0))
        G[v+N*k].append((u+N*(k+1), 0))
dist = dijkstra(0, N*(K+1))
#print(dist)
ans = INF
for k in range(K+1):
    ans = min(ans, dist[N-1+k*N])
if ans==INF:
    print(-1)
else:
    print(ans)