#include <iostream>
#define MAX 53
using namespace std;
int N, M, A[MAX][MAX], B[MAX][MAX], DP[MAX][MAX][MAX][MAX];
int solve (int x1, int y1, int x2, int y2)
{
if (DP[x1][y1][x2][y2] > -1)
return DP[x1][y1][x2][y2];
if (x1 == x2 && y1 == y2)
{
DP[x1][y1][x2][y2] = 0;
return 0;
}
int res = 1073741822;
int n1 = 0;
int n2 = 0;
for (int i = x1; i < x2; i++)
{
n1 = solve(x1,y1,i,y2);
n2 = solve(i + 1,y1,x2,y2);
if (n1 + n2 < res)
res = n1 + n2;
}
for (int i = y1; i < y2; i++)
{
n1 = solve(x1,y1,x2,i);
n2 = solve(x1,i + 1,x2,y2);
if (n1 + n2 < res)
res = n1 + n2;
}
res += B[x2][y2] - B[x1 - 1][y2] - B[x2][y1 - 1] + B[x1 - 1][y1 - 1];
DP[x1][y1][x2][y2] = res;
return res;
}
int main()
{
cin >> N >> M;
for (int i = 1; i <= N; i++)
for (int j = 1; j <= M; j++)
{
cin >> A[i][j];
B[i][j] = A[i][j] + B[i - 1][j] + B[i][j - 1] - B[i - 1][j - 1];
}
for (int i = 1; i <= N; i++)
for (int j = 1; j <= M; j++)
for (int k = 1; k <= N; k++)
for (int l = 1; l <= M; l++)
DP[i][j][k][l] = -1;
cout << solve (1, 1, N, M);
return 0;
}
