import heapq
H,W=map(int,input().split())
A=[]
for _ in range(H):
    A.append(list(map(int,input().split())))
hq=[[] for _ in range(2)]
heapq.heappush(hq[0],(A[0][0],0,0))
heapq.heappush(hq[1],(A[-1][-1],H-1,W-1))
use=[[-1]*W for _ in range(H)]
d=[[1,0],[-1,0],[0,1],[0,-1]]
flag=[[[False]*W for _ in range(H)] for _ in range(2)]
count=0
while True:
    p,x,y=heapq.heappop(hq[count%2])
    if use[x][y]!=-1:
        continue
    use[x][y]=count%2
    for x_d,y_d in d:
        x_m=x+x_d
        y_m=y+y_d
        if 0<=x_m<H and 0<=y_m<W :
            if use[x_m][y_m]==1-count%2:
                print(count-1)
                exit(0)
            elif use[x_m][y_m]==-1 and (not flag[count%2][x_m][y_m]):
                heapq.heappush(hq[count%2],(A[x_m][y_m],x_m,y_m))
                flag[count%2][x_m][y_m]=True
    count+=1