from heapq import heapify, heappop, heappush
H, W, N = map(int, input().split())
G = [[] for _ in range(2 * N + 2)]
G[0].append((2 * N + 1, H - 1 + W - 1))
P = []
for _ in range(N):
    a, b, c, d = map(int, input().split())
    a -= 1; b -= 1; c -= 1; d -= 1
    P.append((a, b, c, d))
for i, (a, b, c, d) in enumerate(P):
    G[0].append((2 * i + 1, a + b))
    G[2 * i + 1].append((2 * i + 2, 1))
    G[2 * i + 2].append((2 * N + 1, H - 1 - c + W - 1 - d))
    for j, (e, f, g, h) in enumerate(P):
        if a == e and b == f: continue
        G[2 * i + 2].append((2 * j + 1, abs(c - e) + abs(d - f)))
dist = [10 ** 18] * (2 * N + 2)
dist[0] = 0
pq = [(0, 0)]
heapify(pq)
while len(pq) > 0:
    d, u = heappop(pq)
    for v, c in G[u]:
        if dist[v] > dist[u] + c:
            dist[v] = dist[u] + c
            heappush(pq, (dist[v], v))
print(dist[2 *N + 1])