import heapq
N,M,K = map(int,input().split())
C = [0]+list(map(int,input().split()))
G = {i:[] for i in range(1,(K+1)*N+1)}
for i in range(1,M+1):
    u,v = map(int,input().split())
    G[u].append((v,C[i]))
    G[v].append((u,C[i]))
    for k in range(1,K+1):
        G[u+k*N].append((v+k*N,C[i]))
        G[v+k*N].append((u+k*N,C[i]))
        G[u+k*N].append((v+(k-1)*N,0))
        G[v+k*N].append((u+(k-1)*N,0))
INFTY = 10**14+100
dist = [INFTY]*((K+1)*N+1)
dist[1+K*N] = 0
que = [(0,1+K*N)]
while que:
    d,x = heapq.heappop(que)
    if dist[x]<d:continue
    for y,c in G[x]:
        if dist[y]>d+c:
            dist[y] = d+c
            heapq.heappush(que,(d+c,y))
ans = dist[N]
for i in range(1,K+1):
    ans = min(ans,dist[i*N])
if ans>=INFTY:
    print(-1)
else:
    print(ans)