#!/usr/bin/env python3
import sys
import threading
import heapq

INF = 10**30

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

adj = [[] for _ in range(N + 1)]
for i in range(M):
    u, v = map(int, input().split())
    c = costs[i]
    adj[u].append((v, c))
    adj[v].append((u, c))

dist = [[INF] * (K + 1) for _ in range(N + 1)]
dist[1][0] = 0

pq = [(0, 1, 0)]

while pq:
    cost_so_far, u, used = heapq.heappop(pq)
    if cost_so_far > dist[u][used]:
        continue
    for v, w in adj[u]:
        nc = cost_so_far + w
        if nc < dist[v][used]:
            dist[v][used] = nc
            heapq.heappush(pq, (nc, v, used))
        if used < K:
            if cost_so_far < dist[v][used + 1]:
                dist[v][used + 1] = cost_so_far
                heapq.heappush(pq, (cost_so_far, v, used + 1))

ans = min(dist[N])
print(ans if ans < INF else -1)