from heapq import heappush, heappop

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

INF = 10**18

def dijkstra(start):
    dist = [[INF]*(K+1) for _ in range(N)]
    dist[start][0] = 0
    visited = [[False]*(K+1) for _ in range(N)]
    que = [(0, start, 0)]
    while que:
        d, now, c = heappop(que)
        if visited[now][c]:
            continue
        visited[now][c] = True
        for next, weight in G[now]:
            if dist[now][c]+weight < dist[next][c]:
                dist[next][c] = dist[now][c]+weight
                heappush(que, (dist[next][c], next, c))
            if c < K and dist[now][c] < dist[next][c+1]:
                dist[next][c+1] = dist[now][c]
                heappush(que, (dist[next][c+1], next, c+1))
    return dist

dist = dijkstra(0)
ans = min(dist[-1])

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