from heapq import heappush, heappop
import math

def solve():
    N, M, K = map(int, input().split())
    C = list(map(int, input().split()))
    
    graph = [[] for _ in range(N + 1)]
    for i in range(M):
        u, v = map(int, input().split())
        graph[u].append((v, C[i]))
        graph[v].append((u, C[i]))
    
    dist = [[math.inf] * (K + 1) for _ in range(N + 1)]
    dist[1][K] = 0  
    
    pq = [(0, 1, K)]
    while pq:
        cost, v, k = heappop(pq)
        
        if cost > dist[v][k]:
            continue
        
        for u, c in graph[v]:
            if dist[u][k] > cost + c:
                dist[u][k] = cost + c
                heappush(pq, (cost + c, u, k))
            
            if k > 0 and dist[u][k - 1] > cost:
                dist[u][k - 1] = cost
                heappush(pq, (cost, u, k - 1))
    
    min_cost = min(dist[N])
    if min_cost == math.inf:
        print(-1)
    else:
        print(min_cost)

solve()