#include <iostream>
#define MAX 51
using namespace std;
int N, M, A[MAX][MAX], B[MAX][MAX][MAX][MAX], C[MAX][MAX];
int solve (short int i1, short int j1, short int i2, short int j2)
{
//cout << i1 << " " << j1 << " " << i2 << " " << j2 << endl;
if (i1 == i2 && j1 == j2)
return 0;
if (B[i1][j1][i2][j2] > 0)
return B[i1][j1][i2][j2];
int res = 1000000000;
for (int i = i1; i < i2; i++)
{
res = min (res, (solve(i1, j1, i, j2) + solve(i + 1, j1, i2, j2)));
}
for (int j = j1; j < j2; j++)
{
res = min (res, (solve(i1, j1, i2, j) + solve(i1, j + 1, i2, j2)));
}
B[i1][j1][i2][j2] = res + C[i2][j2] - C[i1-1][j2] - C[i2][j1-1] + C[i1-1][j1-1];
return B[i1][j1][i2][j2];
}
int main()
{
cin >> N >> M;
for (int i = 1; i <= N; i++)
{
for (int j = 1; j <= M; j++)
{
cin >> A[i][j];
C[i][j] = A[i][j] + C[i-1][j] + C[i][j-1] - C[i-1][j-1];
}
}
cout << solve (1,1,N,M);
return 0;
}
