import heapq
inf = 10**17
def dijkstra(s):
    hq=[]
    heapq.heappush(hq,(0,s))
    dist=[inf for _ in range(N*(K+1))]
    while len(hq)!=0:
        d,p=heapq.heappop(hq)
        if dist[p] < d:
            continue
        dist[p]=d
        for e,c in edge[p]:
            if dist[e]>d+c:
                dist[e]=d+c
                heapq.heappush(hq,(d+c,e))
    return dist

N,M,K=map(int,input().split())
C=list(map(int,input().split()))
edge=[[] for _ in range(N*(K+1))]
for j in range(M):
    u,v=map(int,input().split())
    u-=1
    v-=1
    for i in range(K+1):
        edge[i*N+u].append((i*N+v,C[j]))
        edge[i*N+v].append((i*N+u,C[j]))
    for i in range(K):
        edge[i*N+u].append(((i+1)*N+v,0))
        edge[i*N+v].append(((i+1)*N+u,0))
dist = dijkstra(0)
ans=inf
for i in range(K+1):
    ans=min(ans,dist[i*N+N-1])
if ans==inf:
    print(-1)
else:
    print(ans)