#ifndef LOCAL
#pragma GCC optimize("O3,unroll-loops")
#endif
#include <bits/stdc++.h>
#define fi first
#define se second
#define pn printf("\n")
#define ssize(x) int(x.size())
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define bitcount(x) __builtin_popcount(x)
#define clz(x) __builtin_clz(x)
#define ctz(x) __builtin_ctz(x)
#define mp make_pair
//~ #define r(x) resize(x)
//~ #define rf(x, c) resize(x, c)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<int, ll> pil;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
typedef double db;
typedef long double ldb;
#define V vector
int inf = 2e09; ll infll = 2e18; int mod = (1<<23)*119+1;
int add(int a, int b){return a+b >= mod ? a+b - mod : a+b;}
int sub(int a, int b){return a-b < 0 ? a-b + mod : a-b;}
int mul(int a, int b){return int(a * ll(b) % mod);}
int fpow(int a, ll b){
int ret = 1;
while(b){
if(b & 1) ret = mul(ret, a);
b >>= 1, a = mul(a, a);
} return ret;
}
int inv(int a){ return fpow(a, mod-2); }
struct coeff{
V<int> fac, invfac;
coeff(int n){
fac.resize(n+1), invfac.resize(n+1);
fac[0] = 1, invfac[0] = 1;
for(int i = 1; i <= n; ++i) fac[i] = mul(fac[i-1], i);
invfac[n] = inv(fac[n]);
for(int i = n-1; i; --i) invfac[i] = mul(invfac[i+1], i+1);
}
int get(int n, int k){
if(n < k) return 0;
return mul(fac[n], mul(invfac[n-k], invfac[k]));
}
};
void answer(){
int n, m; scanf("%d%d", &n, &m);
V<V<int>> t(n+1, V<int>(m+1, 0));
for(int i = 1; i <= n; ++i)
for(int j = 1; j <= m; ++j) scanf("%d", &t[i][j]);
int mn = inf, mx = 0;
for(int i = 1; i <= n; ++i)
for(int j = 1; j <= m; ++j)
mn = min(mn, t[i][j]), mx = max(mx, t[i][j]);
auto calc = [&](){
int result = inf;
V<V<pii>> p(n+1, V<pii>(m+2, pii(0, 0)));
for(int i = 1; i <= n; ++i){
for(int j = 1; j <= m; ++j)
p[i][j].fi = max(p[i][j-1].fi, t[i][j]-mn);
for(int j = m; j >= 1; --j)
p[i][j-1].se = max(p[i][j+1].se, mx-t[i][j]);
}
V<V<int>> dp(n+1, V<int>(m+2, inf));
for(int i = 0; i <= m; ++i) dp[0][i] = 0;
for(int i = 1; i <= n; ++i){
for(int j = 0; j <= m; ++j){
for(int l = j; l <= m; ++l) dp[i][j] = min(dp[i][j], dp[i-1][l]);
dp[i][j] = max(dp[i][j], max(p[i][j].fi, p[i][j].se));
}
}
// pn;
// // printf("%d %d\n\n", mn, mx);
// for(int i = 1; i <= n; ++i){
// for(int j = 0; j <= m; ++j) printf("%d %d,", p[i][j].fi, p[i][j].se);
// pn;
// }
// pn;
for(int i = 0; i <= m; ++i)
result = min(result, dp[n][i]);
dp = V<V<int>>(n+1, V<int>(m+2, inf));
for(int i = 0; i <= m; ++i) dp[0][i] = 0;
for(int i = 1; i <= n; ++i){
for(int j = 0; j <= m; ++j){
for(int l = 0; l <= j; ++l) dp[i][j] = min(dp[i][j], dp[i-1][l]);
dp[i][j] = max(dp[i][j], max(p[i][j].fi, p[i][j].se));
}
}
for(int i = 0; i <= m; ++i)
result = min(result, dp[n][i]);
// for(int i = 1; i <= n; ++i){
// for(int j = 0; j <= m; ++j) printf("%d ", dp[i][j]);
// pn;
// }
return result;
};
int result = mx-mn;
result = min(result, calc());
for(int i = 1; i <= n; ++i) reverse(1+all(t[i]));
result = min(result, calc());
printf("%d\n", result);
}
int main(){
int T = 1;
// scanf("%d", &T);
//~ ios_base::sync_with_stdio(0); cin.tie(0); cin >> T;
for(++T; --T; ) answer();
return 0;
}
