import heapq

N, M, K = map(int, input().split())
C = list(map(int, input().split()))

edges = [[[] for _ in range(K+1)] for _ in range(N)]

for i in range(M):
    u, v = map(int, input().split())
    u -= 1
    v -= 1
    for j in range(K+1):
        edges[u][j].append((v, j, C[i]))
        edges[v][j].append((u, j, C[i]))
    for j in range(K):
        edges[u][j].append((v, j+1, 0))
        edges[v][j].append((u, j+1, 0))

def dijkstra(start, end):
    dist = [[float('inf')] * (K+1) for _ in range(N)]
    dist[start][0] = 0
    pq = [(0, start, 0)]

    while pq:
        d, u, k = heapq.heappop(pq)
        if d > dist[u][k]:
            continue
        for v, nk, cost in edges[u][k]:
            nd = d + cost
            if nd < dist[v][nk]:
                dist[v][nk] = nd
                heapq.heappush(pq, (nd, v, nk))

    return min(dist[end])

result = dijkstra(0, N-1)
if result == float('inf'):
    print(-1)
else:
    print(result)