from heapq import heapify, heappop, heappush
H, W, N = map(int, input().split())
D = {}
for _ in range(N):
    a, b, c, d = map(int, input().split())
    a -= 1; b -= 1; c -= 1; d -= 1
    D[(a, b)] = (c, d)
dist = [10 ** 18] * (H * W)
dist[0] = 0
pq = [(0, 0)]
heapify(pq)
dx = [-1, 0, 0, 1]
dy = [0, -1, 1, 0]
while len(pq) > 0:
    d, id = heappop(pq)
    x, y = id // W, id % W
    if (x, y) in D:
        v, w = D[(x, y)]
        if dist[v * W + w] > dist[id] + 1:
            dist[v * W + w] = dist[id] + 1
            heappush(pq, (dist[v * W + w], v * W + w))
    for i in range(4):
        nx = x + dx[i]
        ny = y + dy[i]
        if 0 > nx or nx >= H or 0 > ny or ny >= W: continue
        if dist[nx * W + ny] > dist[id] + 1:
            dist[nx * W + ny] = dist[id] + 1
            heappush(pq, (dist[nx * W + ny], nx * W + ny))
print(dist[(H - 1) * W + (W - 1)])