#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int H,W,N;
int C[1010][1010];
int D[1010][1010];
vector<pair<int,int>> cand[1010101];
int pat[1010101];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>H>>W>>N;
	FOR(y,H) FOR(x,W) {
		cin>>C[y][x];
		cand[C[y][x]].push_back({y,x});
	}
	int ret=0;
	pat[0]=1;
	FOR(i,N+1) if(cand[i].size()) {
		int ma=pat[i-1];
		FORR2(y,x,cand[i]) {
			FOR(j,4) {
				int d[4]={0,1,0,-1};
				int ty=y+d[j];
				int tx=x+d[j^1];
				if(ty<0||ty>=H||tx<0||tx>=W) continue;
				if(C[ty][tx]>=C[y][x]) continue;
				ma=max(ma,D[ty][tx]+1);
			}
		}
		FORR2(y,x,cand[i]) D[y][x]=ma;
		pat[i]=ma;
		ret=max(ret,ma);
	}
	cout<<ret<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}