#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1'000'000'000'000'000;
ll total_sum[51][51][51][51];
ll dp[51][51][51][51];
ll arr[51][51];
int main()
{
int N, M;
cin >> N >> M;
for (int i=0; i<N; i++)
for (int j=0; j<M; j++)
{
cin >> arr[i][j];
total_sum[i][i][j][j] = arr[i][j];
}
for (int diffi=0; diffi<N; diffi++)
for (int diffj=0; diffj<N; diffj++)
{
for (int i=0; i<(N-diffi); i++)
for (int j=0; j<(N-diffj); j++)
{
int hi_i = i+diffi;
int hi_j = j+diffj;
ll total = 0;
ll ans = INF;
for (int cut_i = i; cut_i<hi_i; cut_i++)
{
total = total_sum[i][cut_i][j][hi_j] + total_sum[cut_i+1][hi_i][j][hi_j];
ans = min(ans, total + dp[i][cut_i][j][hi_j] + dp[cut_i+1][hi_i][j][hi_j]);
}
for (int cut_j = j; cut_j<hi_j; cut_j++)
{
total = total_sum[i][hi_i][j][cut_j] + total_sum[i][hi_i][cut_j+1][hi_j];
ans = min(ans, total + dp[i][hi_i][j][cut_j] + dp[i][hi_i][cut_j+1][hi_j]);
}
dp[i][hi_i][j][hi_j] = ans;
if ((i!=hi_i) or (j!=hi_j))
total_sum[i][hi_i][j][hi_j] = total;
}
}
cout << dp[0][N-1][0][M-1] << '\n';
}
