#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define INF 1000
using namespace std;
int s[101][101]={0};
int c[101][101]={0},n,ans=1000;
void dfs(int x,int y,int t,int d){
	if (c[x][y]<t) return;
	s[x][y]=d;
	if (x<n && max(s[x][y],c[x+1][y])<s[x+1][y]) dfs(x+1,y,t,max(s[x][y],c[x+1][y]));
	if (x>1 && max(s[x][y],c[x-1][y])<s[x-1][y]) dfs(x-1,y,t,max(s[x][y],c[x-1][y]));
	if (y<n && max(s[x][y],c[x][y+1])<s[x][y+1]) dfs(x,y+1,t,max(s[x][y],c[x][y+1]));
	if (y>1 && max(s[x][y],c[x][y-1])<s[x][y-1]) dfs(x,y-1,t,max(s[x][y],c[x][y-1]));
	return;
}
int main(){
	freopen("adven.in","r",stdin);
	freopen("adven.out","w",stdout);
	scanf("%d",&n);
	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++){
			scanf("%d",&c[i][j]);
		}
	}
	for (int i=0;i<=n;i++){
		memset(s,1,sizeof(s));
		dfs(1,1,i,0);
		ans=min(ans,s[n][n]-i);
	}
	printf("%d",ans);
	return 0;
}