from heapq import heappush,heappop
H,W,N = map(int,input().split())

ten = {}
cnt = 1
warp = {}

ten[(1,1)] = 1
cnt += 1
for i in range(N):
    a,b,c,d = map(int,input().split()) #a=頂点,b=頂点,c=コスト
    if (a,b) not in ten:
        ten[(a,b)] = cnt
        cnt+=1
    if (c,d) not in ten:
        ten[(c,d)] = cnt
        cnt+=1
    
    warp[(a,b,c,d)] = True

ten[(H,W)] = cnt

G = [[] for _ in range(cnt+1)]

for ind1,val1 in ten.items():
    for ind2,val2 in ten.items():
        if val1 == val2:
            continue
        aa,bb,cc,dd = ind1[0],ind1[1],ind2[0],ind2[1]
        if (aa,bb,cc,dd) in warp:
            G[val1].append([val2,1])
        else:
            cost = abs(aa-cc) + abs(bb-dd)
            G[val1].append([val2,cost])

dist = [-1]*(cnt+1)
visited = [False]*(cnt+1)

Q = []
heappush(Q,(0,1)) #◆=出発地点コスト（通常は0）,◇=出発地点の頂点
dist[1] = 0

while len(Q)>0:
    a,b = heappop(Q) #a=コスト(◆),b=頂点(◇)

    if visited[b]:
        continue

    visited[b] = True

    for c,d in G[b]: #c=頂点,d=コスト
        if dist[c] == -1 or dist[c] > dist[b]+d:
            dist[c] = dist[b]+d
            heappush(Q,(dist[c],c))

print(dist[-1])