import heapq
import sys

def dijkstra(n, m, k, bridges, costs):
    INF = sys.maxsize
    min_cost = [[INF] * (k + 1) for _ in range(n + 1)]
    min_cost[1][0] = 0
    pq = [(0, 1, 0)]

    while pq:
        cost, city, coupons_used = heapq.heappop(pq)

        if cost > min_cost[city][coupons_used]:
            continue

        for i in range(m):
            u, v = bridges[i]
            c = costs[i]
            if city == u:
                next_city = v
            elif city == v:
                next_city = u
            else:
                continue

            if cost + c < min_cost[next_city][coupons_used]:
                min_cost[next_city][coupons_used] = cost + c
                heapq.heappush(pq, (cost + c, next_city, coupons_used))

            if coupons_used < k and cost < min_cost[next_city][coupons_used + 1]:
                min_cost[next_city][coupons_used + 1] = cost
                heapq.heappush(pq, (cost, next_city, coupons_used + 1))

    result = min(min_cost[n][i] for i in range(k + 1))
    return result if result != INF else -1

n, m, k = map(int, input().split())
costs = list(map(int, input().split()))
bridges = [tuple(map(int, input().split())) for _ in range(m)]

result = dijkstra(n, m, k, bridges, costs)
print(result)