import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

from heapq import *
INF = 10**18
def dijkstra(g, s, n):
    dist = [INF]*n
    hq = [(0, s)]
    dist[s] = 0
    while hq:
        d, v = heappop(hq)
        if dist[v]!=d:
            continue
        for to, c in g[v]:
            if dist[v] + c < dist[to]:
                dist[to] = dist[v] + c
                heappush(hq, (dist[to], to))
    return dist

n, m, k = na()
c = na()

N = n * (k + 1)
G = [[] for i in range(N)]

for i in range(m):
    u, v = na()
    u -= 1
    v -= 1
    for j in range(k):
        G[u + n * j].append((v + n * (j + 1), 0))
        G[v + n * j].append((u + n * (j + 1), 0))
    for j in range(k+1):
        G[u + n * j].append((v + n * j, c[i]))
        G[v + n * j].append((u + n * j, c[i]))

ans = INF
dist = dijkstra(G, 0, N)
for i in range(k + 1):
    ans = min(ans, dist[n - 1 + n * i])
if ans == INF:
    print(-1)
else:
    print(ans)