n, m = map(int, input().split())
edges = [[] for _ in range(n)]
for _ in range(m):
    u, v, w = map(int, input().split())
    edges[u - 1].append((v - 1, w))

ng = set()
k = int(input())
for _ in range(k):
    a, b, c = map(int, input().split())
    a -= 1
    b -= 1
    c -= 1
    ng.add((a, b, c))

cand = [[] for _ in range(n)]
cand[0] = [(0, 0)]
for l in range(n):
    cand[l].sort(key=lambda x: x[0])
    for d, a in cand[l]:
        nex = []
        for r, w in edges[l]:
            if (a, l, r) in ng:
                nex.append((r, w))
            else:
                cand[r].append((d + w, l))

        edges[l] = nex

ans = 1 << 60
for d, _ in cand[n - 1]:
    ans = min(ans, d)

if ans == 1 << 60:
    print(-1)
else:
    print(ans)