from heapq import *
N,M,K = map(int,input().split())
C = list(map(int,input().split()))
INF = 10 ** 16
KN = K * N
E = [[] for _ in range(N)]
for i in range(M):
    u,v = map(int,input().split())
    u -= 1
    v -= 1
    E[u].append((v,i))
    E[v].append((u,i))

D = [INF] * ((K+1) * N)
D[0] = 0

def dijkstra():
    q = [(0,0)]
    while q:
        d, u1 = heappop(q)
        if d > D[u1]: continue
        k = u1 // N
        u = u1 % N
        for v,i in E[u]:
            if k < K:
                a = v + N * (k + 1)
                if D[a] > D[u1]:
                    D[a] = D[u1]
                    heappush(q, (D[a], a))
            a = v + k * N
            if D[a] > D[u1] + C[i]:
                D[a] = D[u1] + C[i]
                heappush(q, (D[a], a))
    return

dijkstra()
ans = INF
for i in range(1,K+2):
    ans = min(ans,D[N * i - 1])

if ans == INF:
    print(-1)
else:
    print(ans)