#include <bits/stdc++.h>
using namespace std;
const int MAX = 69;
const int inf = 1e9 + 69;
int N, M;
int pfx[MAX][MAX];
int dp[MAX][MAX][MAX][MAX];
inline int sum(int r1, int c1, int r2, int c2)
{
return pfx[r2][c2] - pfx[r1-1][c2] - pfx[r2][c1-1] + pfx[r1-1][c1-1];
}
inline int solve(int r1, int c1, int r2, int c2)
{
if (r1 == r2 && c1 == c2)
return 0;
if (dp[r1][c1][r2][c2] != inf)
return dp[r1][c1][r2][c2];
for (int i = r1; i < r2; ++i)
dp[r1][c1][r2][c2] = min(dp[r1][c1][r2][c2], sum(r1, c1, r2, c2) + solve(r1, c1, i, c2) + solve(i+1, c1, r2, c2));
for (int i = c1; i < c2; ++i)
dp[r1][c1][r2][c2] = min(dp[r1][c1][r2][c2], sum(r1, c1, r2, c2) + solve(r1, c1, r2, i) + solve(r1, i+1, r2, c2));
return dp[r1][c1][r2][c2];
}
int main()
{
ios :: sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> N >> M;
for (int i = 1; i <= N; ++i)
for (int j = 1; j <= M; ++j)
cin >> pfx[i][j], pfx[i][j] += pfx[i-1][j] + pfx[i][j-1] - pfx[i-1][j-1];
for (int i = 1; i <= N; ++i)
for (int j = 1; j <= M; ++j)
for (int k = i; k <= N; ++k)
for (int l = j; l <= M; ++l)
dp[i][j][k][l] = inf;
cout << solve(1, 1, N, M) << '\n';
return 0;
}
