h, w, n = map(int, input().split())
V = [0, h * w - 1]
edges = {}
for _ in range(n):
    a, b, c, d = map(int, input().split())
    a -= 1
    b -= 1
    c -= 1
    d -= 1
    x = a * w + b
    y = c * w + d
    V.append(x)
    V.append(y)
    edges.setdefault(x, []).append(y)

V = sorted(set(V))
idx = {v: i for i, v in enumerate(V)}
n = len(V)
dist = [1 << 60] * n
dist[0] = 0
used = [False] * n
for _ in range(n):
    pos = -1
    mi = 1 << 60
    for i in range(n):
        if not used[i] and dist[i] < mi:
            mi = dist[i]
            pos = i
    used[pos] = True

    i1 = V[pos] // w
    j1 = V[pos] - w * i1
    for npos in range(n):
        i2 = V[npos] // w
        j2 = V[npos] - w * i2
        nd = dist[pos] + abs(i1 - i2) + abs(j1 - j2)
        dist[npos] = min(dist[npos], nd)
    for npos in edges.get(V[pos], []):
        nd = dist[pos] + 1
        dist[idx[npos]] = min(dist[idx[npos]], nd)

print(dist[-1])