from collections import defaultdict
import heapq
N,M,K=list(map(int,input().split()))
C=list(map(int,input().split()))
path=defaultdict(list)
for i in range(M):
	u,v=list(map(int,input().split()))
	u-=1
	v-=1
	for j in range(K+1):
		path[u+N*j].append((C[i],v+N*j))
		path[v+N*j].append((C[i],u+N*j))
	for j in range(K):
		path[u+N*j].append((0,v+N*j+N))
		path[v+N*j].append((0,u+N*j+N))
		
dist=[10**18]*(N*K+N)
dist[0]=0
Q=[]
heapq.heapify(Q)
check=set()
heapq.heappush(Q,(0,0))
while len(Q)>0:
	d,p=heapq.heappop(Q)
	if p in check:
		continue
	check.add(p)
	for c,j in path[p]:
		if dist[j]>d+c:
			dist[j]=d+c
			heapq.heappush(Q,(d+c,j))
ans=10**18
for i in range(K+1):
	ans=min(ans,dist[N*i+N-1])
if ans>10**17:
	ans=-1
print(ans)