#include <bits/stdc++.h>
using namespace std;

constexpr int maxn = 110;


int dx[] = {0,0,-1,1};
int dy[] = {-1,1,0,0};
int a[maxn][maxn];
int bio[maxn][maxn];
int n,gmax=-1,gmin=1000;
int cmin, cmax;

bool check(int x, int y){
    return x >= 0 && x < n && y >= 0 && y < n &&
        a[x][y] >= cmin && a[x][y] <= cmax && !bio[x][y];
}

bool solve(){
    queue<pair<int,int>> q;
    q.push(make_pair(0,0));

    while(!q.empty()){
        int x = q.front().first;
        int y = q.front().second;
        if(x == n-1 && y == n-1)
            return true;
        q.pop();
        bio[x][y] = true;
        //printf("nalazim se u %d %d\n",x,y);

        for(int i = 0; i < 4; ++i){
            int sx = x + dx[i];
            int sy = y + dy[i];
           // printf("idem u %d %d\n",sx,sy);
            if(!check(sx,sy)) continue;
            q.push(make_pair(sx,sy));
        }
    }

    return false;
}


int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);

scanf("%d",&n);
for(int i = 0; i < n; ++i){
    for(int j = 0; j < n; ++j){
        scanf("%d",&a[i][j]);
        gmax = max(gmax,a[i][j]);
        gmin = min(gmin,a[i][j]);
    }
}

for(int i = 0; i <= gmax - gmin; ++i){ //iteriranje po svim mogucim razlikama
    for(int j = gmin; j <= gmax - i; ++j){ // isprobavanje postoji li staza za sve moguce intervale duljine i
        cmin = j;
        cmax = j+i;
       // printf("cmin je %d cmax je %d\n",cmin,cmax);
        if(a[0][0] < cmin || a[0][0] > cmax) continue;
        memset(bio,0,sizeof(bio));
        if(solve()){
            cout << i;
            return 0;
        }
    }
}

return 0;
}