## https://yukicoder.me/problems/no/3111

import heapq

MAX_INT = 10 ** 18

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

    queue = []
    seen = [[MAX_INT] * N for _ in range(K + 1)]
    fix = [[MAX_INT] * N for _ in range(K + 1)]
    seen[0][0] = 0
    heapq.heappush(queue, (0, 0, 0))
    while len(queue) > 0:
        cost, count, v = heapq.heappop(queue)
        if fix[count][v] < MAX_INT:
            continue

        fix[count][v] = cost
        for w, c in next_nodes[v]:

            if count + 1 <= K:
                if fix[count + 1][w] == MAX_INT:
                    new_cost = cost
                    if seen[count + 1][w] > new_cost:
                        seen[count + 1][w] = new_cost
                        heapq.heappush(queue, (new_cost, count + 1, w))
            
            if fix[count][w] < MAX_INT:
                continue

            new_cost = cost + c
            if seen[count][w] > new_cost:
                seen[count][w] = new_cost
                heapq.heappush(queue, (new_cost, count, w))
    

    x = MAX_INT
    for c in range(K + 1):
        x = min(x, fix[c][N - 1])

    if x == MAX_INT:
        print(-1)
    else: 
        print(x)


        
    





if __name__ == "__main__":
    main()