h,w,n=map(int,input().split())
c=[[] for i in range(h)]
for i in range(h):
    c[i]=list(map(int,input().split()))
root=[[] for i in range(n+1)]

class topological_sort():
    #1-indexed
    #0-indexedはバグる
    def __init__(self,n):
        self.n=n
        self.root=[[] for _ in range(self.n+1)]
        self.deg=[0]*(self.n+1)
    def add(self,a,b):
        #有向辺 a->b の追加
        self.root[a].append(b)
        self.deg[b]+=1
    def const(self):
        #トポロジカルソートした結果を返す
        #不可能なら [] を返す
        deg2=self.deg[:]
        search=[]
        res=[]
        for i in range(1,self.n+1):
            if deg2[i]==0:search.append(i)
        while search:
            now=search.pop()
            res.append(now)
            for next in self.root[now]:
                deg2[next]-=1
                if deg2[next]==0:
                    search.append(next)
        if len(res)==self.n:
            return res
        return []

delta=[(1,0),(-1,0),(0,1),(0,-1)]
tp=topological_sort(n)
for i in range(h):
    for j in range(w):
        for di,dj in delta:
            if i+di<0 or i+di>=h or j+dj<0 or j+dj>=w:continue
            root[c[i][j]].append(c[i+di][j+dj])

p=tp.const()
p.reverse()
dp=[10**18]*(n+1)
dp[1]=1
for i in range(2,n+1):
    dp[i]=dp[i-1]
    for x in root[i]:
        if x<i:dp[i]=max(dp[i],dp[x]+1)
print(dp[n])