#include <iostream>
#include <vector>
#include <climits>
using namespace std;
int getSum(const vector<vector<int>>& prefixSum, int x1, int y1, int x2, int y2) {
int total = prefixSum[x2 + 1][y2 + 1];
if (x1 > 0) total -= prefixSum[x1][y2 + 1];
if (y1 > 0) total -= prefixSum[x2 + 1][y1];
if (x1 > 0 && y1 > 0) total += prefixSum[x1][y1];
return total;
}
int dp(int x1, int y1, int x2, int y2, vector<vector<vector<vector<int>>>>& memo, const vector<vector<int>>& prefixSum) {
if (x1 == x2 && y1 == y2) return 0;
if (memo[x1][y1][x2][y2] != -1) return memo[x1][y1][x2][y2];
int totalCost = getSum(prefixSum, x1, y1, x2, y2);
int minCost = INT_MAX;
for (int row = x1; row < x2; ++row) {
int topCost = dp(x1, y1, row, y2, memo, prefixSum);
int bottomCost = dp(row + 1, y1, x2, y2, memo, prefixSum);
minCost = min(minCost, topCost + bottomCost);
}
for (int col = y1; col < y2; ++col) {
int leftCost = dp(x1, y1, x2, col, memo, prefixSum);
int rightCost = dp(x1, col + 1, x2, y2, memo, prefixSum);
minCost = min(minCost, leftCost + rightCost);
}
return memo[x1][y1][x2][y2] = totalCost + minCost;
}
int main() {
int N, M;
cin >> N >> M;
vector<vector<int>> chocolate(N, vector<int>(M));
for (int i = 0; i < N; ++i) {
for (int j = 0; j < M; ++j) {
cin >> chocolate[i][j];
}
}
vector<vector<int>> prefixSum(N + 1, vector<int>(M + 1, 0));
for (int i = 0; i < N; ++i) {
for (int j = 0; j < M; ++j) {
prefixSum[i + 1][j + 1] = chocolate[i][j] + prefixSum[i][j + 1] + prefixSum[i + 1][j] - prefixSum[i][j];
}
}
vector<vector<vector<vector<int>>>> memo(N, vector<vector<vector<int>>>(M, vector<vector<int>>(N, vector<int>(M, -1))));
cout << dp(0, 0, N - 1, M - 1, memo, prefixSum) << endl;
return 0;
}
