from collections import defaultdict
from heapq import *

h, w, n = map(int, input().split())
warp = dict()
for _ in range(n):
    a, b, c, d = map(lambda x: int(x) - 1, input().split())
    warp[(a, b)] = (c, d)

q = [[0, 0, 0]]
INF = float("INF")
dist = defaultdict(lambda: INF)
dist[(0, 0)] = 0
while q:
    dis, i, j = heappop(q)
    if (i, j) in dist and dist[(i, j)] != dis:
        continue

    # warpを使う場合
    if (i, j) in warp:
        ti, tj = warp[(i, j)]
        if dist[(ti, tj)] > dist[(i, j)] + 1:
            dist[(ti, tj)] = dist[(i, j)] + 1
            heappush(q, [dist[(ti, tj)], ti, tj])
    # i,j から別のワープ a,b まで移動
    for (a, b), (c, d) in warp.items():
        md = abs(i - a) + abs(j - b)
        if dist[(a, b)] > dist[(i, j)] + md:
            dist[(a, b)] = dist[(i, j)] + md
            heappush(q, [dist[(a, b)], a, b])
    # H,Wまで移動
    md = abs(i - h + 1) + abs(j - w + 1)
    if dist[(h - 1, w - 1)] > dist[(i, j)] + md:
        dist[(h - 1, w - 1)] = dist[(i, j)] + md
        heappush(q, [dist[((h - 1, w - 1))], h - 1, w - 1])
print(dist[(h - 1, w - 1)])