from collections import deque
H,W,N=map(int,input().split())
WARP={}
for _ in range(N):
    a,b,c,d=map(int,input().split())
    a-=1;b-=1;c-=1;d-=1
    WARP[(a,b)]=(c,d)
G=[[10**10 for _ in range(W)] for _ in range(H)]
Q=deque([])
Q.append(((0,0),0))
while Q:
    (h,w),c=Q.popleft()
    c=min(c,G[h][w])
    G[h][w]=c
    if h+1<H and c+1<G[h+1][w]:Q.append(((h+1,w),c+1))
    if w+1<W and c+1<G[h][w+1]:Q.append(((h,w+1),c+1))
    if (h,w) in WARP.keys():
        nh,nw=WARP[(h,w)]
        if c+1<G[nh][nw]:Q.append((WARP[(h,w)],c+1))
print(G[H-1][W-1])