/**
* author: Duarte Nobrega
* created: 29.05.2020
**/
#include <bits/stdc++.h>
using namespace std;
const int N = 50 + 5;
int g [N][N], s [N][N];
int dp [N][N][N][N];
int r, c;
int solve (int x1, int y1, int x2, int y2) {
if (x1 > x2) return 0;
if (y1 > y2) return 0;
if (x1 == x2 && y1 == y2) return 0;
int &res = dp[x1][y1][x2][y2];
if (~res) return res;
res = 1e9;
for (int i = x1; i <= x2; i++) {
int other = solve (x1, y1, i, y2) + solve (i + 1, y1, x2, y2);
res = min (res, other);
}
for (int i = y1; i <= y2; i++) {
int other = solve (x1, y1, x2, i) + solve (x1, i + 1, x2, y2);
res = min (res, other);
}
return res += s[x2][y2] - (x1 - 1 >= 0 ? s[x1 - 1][y2] : 0) - (y1 - 1 >= 0 ? s[x2][y1 - 1] : 0) + (x1 - 1 >= 0 && y1 - 1 >= 0 ? s[x1 - 1][y1 - 1] : 0);
}
int main () {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> r >> c;
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
cin >> g[i][j];
}
}
s[0][0] = g[0][0];
for (int i = 1; i < c; i++) s[0][i] = s[0][i - 1] + g[0][i];
for (int i = 1; i < r; i++) s[i][0] = s[i - 1][0] + g[i][0];
for (int i = 1; i < r; i++) {
for (int j = 1; j < c; j++) {
s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + g[i][j];
}
}
memset (dp, -1, sizeof(dp));
cout << solve (0, 0, r - 1, c - 1) << '\n';
return 0;
}
