#include <bits/stdc++.h>
using namespace std;
int n,p[710][710],m,s,fa[600010],e,si[600010],dx[4]={-1,0},dy[4]={0,-1};
inline int read(){
    int x=0,y=1;
    char ch=getchar();
    while(!isdigit(ch)){if(ch=='-')y=-y; ch=getchar();}
    while(isdigit(ch)){x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
    return x*y;
}
struct node{
    int zhi,x,y;
}a[250010];
bool check(int x,int y){
    if(x>0&&x<=n&&y>0&&y<=n)
        return true;
    return false;
}
bool cmp(node x,node y){
    return x.zhi<y.zhi;
}
int Find(int x){
    int root=x;
    while(root!=fa[root])
        root=fa[root];
    while(x!=root){
        int tmp=fa[x];
        fa[x]=root;
        x=tmp;
    }
    return root;
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            p[i][j]=read();
            e++;
            fa[e]=e;
            si[e]=1;
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            for(int k=0;k<2;k++){
                int nx=i+dx[k],ny=j+dy[k];
                if(check(nx,ny)){
                    s++;
                    a[s].x=(i-1)*n+j;
                    a[s].y=(nx-1)*n+ny;
                    a[s].zhi=abs(p[nx][ny]-p[i][j]);
                }
            }
        }
    }
    sort(a+1,a+s+1,cmp);
    for(int i=1;i<=s;i++){
        int fx=Find(a[i].x),fy=Find(a[i].y);
        if(fx!=fy){
            fa[fx]=fy;
            si[fy]+=si[fx];
            if(si[fy]>=(n*n+1)/2){
                cout<<a[i].zhi;
                return 0;
            }
        }
    }
}