from heapq import heappop as pop, heappush as push

N, M, K = map(int, input().split())
C = list(map(int, input().split()))
uv = [map(int, input().split()) for _ in range(M)]

edges = [[] for _ in range(N*4)]

for c, (u, v) in zip(C, uv):
    u -= 1
    v -= 1
    for i in range(K+1):
        edges[i*N+u].append((i*N+v, c))
        edges[i*N+v].append((i*N+u, c))
        if i:
            edges[(i-1)*N+u].append((i*N+v, 0))
            edges[(i-1)*N+v].append((i*N+u, 0))

dist = [float("inf")]*(N*(K+1))
pq = [(0, 0)]
dist[0] = 0

while pq:
    c, v = pop(pq)
    if dist[v] < c:
        continue
    if v%N == N-1:
        print(c)
        break
    for u, bc in edges[v]:
        if dist[u] <= c + bc:
            continue
        dist[u] = c+bc
        push(pq, (c+bc, u))
else:
    print(-1)