#include <bits/stdc++.h>
// author : aykhn
using namespace std;
typedef long long ll;
#define pb push_back
#define ins insert
#define mpr make_pair
#define all(v) v.begin(), v.end()
#define bpc __builtin_popcount
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second
#define int ll
#define infll 0x3F3F3F3F3F3F3F3F
#define inf 0x3F3F3F3F
const int MXN = 55;
int n, m;
int dp[MXN][MXN][MXN][MXN];
int pref[MXN][MXN];
int a[MXN][MXN];
int sum(int i1, int j1, int i2, int j2)
{
int x = pref[i1 - 1][j2];
int y = pref[i2][j1 - 1];
return pref[i2][j2] - x - y + pref[i1 - 1][j1 - 1];
}
int f(int i1, int j1, int i2, int j2)
{
if (i1 == i2 && j1 == j2) return 0;
if (dp[i1][j1][i2][j2] != -1) return dp[i1][j1][i2][j2];
int res = inf;
int id = -1;
for (int k = j1; k < j2; k++)
{
int x = f(i1, j1, i2, k) + f(i1, k + 1, i2, j2);
if (x < res)
{
id = k;
res = x;
}
}
for (int k = i1; k < i2; k++)
{
int x = f(i1, j1, k, j2) + f(k + 1, j1, i2, j2);
if (x < res)
{
id = -k;
res = x;
}
}
return dp[i1][j1][i2][j2] = res + sum(i1, j1, i2, j2);
}
void _()
{
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
cin >> a[i][j];
for (int k = 1; k <= n; k++)
{
for (int l = 1; l <= m; l++)
{
dp[i][j][k][l] = -1;
}
}
}
}
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
pref[i][j] = pref[i - 1][j] + pref[i][j - 1] - pref[i - 1][j - 1] + a[i][j];
}
}
cout << f(1, 1, n, m) << '\n';
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
for (int i = 1; i <= t; i++)
{
_();
}
}
