import heapq
N,M,K = list(map(int,input().split()))
C = list(map(int,input().split()))
edge = [[] for _ in range(N)]
for i in range(M):
    u,v = list(map(int,input().split()))
    u -= 1;v -= 1
    edge[u].append((v,C[i]))
    edge[v].append((u,C[i]))

INF = 10**18
visited = [[INF for _ in range(K+1)] for _ in range(N)]
q = [(0,0,0)]
while(q):
    cost,pon,now = heapq.heappop(q)

    if(now == N-1):
        print(cost)
        exit()

    if(visited[now][pon] <= cost):continue
    visited[now][pon] = cost
    
    for v,w in edge[now]:
        if(visited[v][pon] <= cost+w):continue
        heapq.heappush(q,(cost+w,pon,v))
    
    if(pon != K):
        for v,w in edge[now]:
            if(visited[v][pon+1] <= cost):continue
            heapq.heappush(q,(cost,pon+1,v))

print(-1)