//
// IOI2009Salesman.cpp
//
//
// Created by Matjaz Leonardis on 11/11/2023.
//
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <string.h>
using namespace std;
int N,M;
int R[55][55];
int INF = (1<<31) - 1;
int dp[50][50][50][50];
int S[55][55];
int sum(int x0, int y0, int x1, int y1){
if (x0 == 0 && y0 == 0) return S[x1][y1];
if (x0 == 0) return S[x1][y1] - S[x1][y0 -1];
if (y0 == 0) return S[x1][y1] - S[x0 - 1][y1];
return S[x1][y1] - S[x0-1][y1] - S[x1][y0 -1] + S[x0-1][y0-1];
}
int solve(int x0, int y0, int x1, int y1){
if (x0 == x1 && y0 == y1) return 0;
if (dp[x0][y0][x1][y1] != -1) return dp[x0][y0][x1][y1];
int best = INF;
for (int xn=x0;xn<x1;xn++){
int tmp = solve(x0, y0, xn, y1) + solve(xn+1, y0, x1, y1);
best = min(best, tmp);
}
for (int yn=y0;yn<y1;yn++){
int tmp = solve(x0, y0, x1, yn) + solve(x0, yn + 1, x1, y1);
best = min(best, tmp);
}
return dp[x0][y0][x1][y1] = best + sum(x0, y0, x1, y1);
}
int main(){
memset(dp, -1, sizeof(dp));
cin >> N >> M;
for (int i=0;i<N;i++){
for (int j=0;j<M;j++) cin >> R[i][j];
}
S[0][0] = R[0][0];
for (int i=1;i<M;i++) S[0][i] = S[0][i-1] + R[0][i];
for (int i=1;i<N;i++) S[i][0] = S[i-1][0] + R[i][0];
for (int i=1;i<N;i++){
for (int j=1;j<M;j++) S[i][j] = S[i-1][j] + S[i][j-1] - S[i-1][j-1] + R[i][j];
}
cout << solve(0,0,N-1,M-1) << endl;
return 0;
}
