#include <iostream>
#define MAXN 50
using namespace std;
int dp[MAXN + 1][MAXN + 1][MAXN + 1][MAXN + 1]; // minimum cost to cut ijkl rectangle
int numr[MAXN + 1][MAXN + 1];
int main() {
int N, M;
cin >> N >> M;
for (int i = 0; i <= MAXN; i++) {
for (int j = 0; j <= MAXN; j++) {
for (int k = 0; k <= MAXN; k++) {
fill(dp[i][j][k], dp[i][j][k] + MAXN + 1, 2500001);
}
}
}
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= M; j++) {
cin >> numr[i][j];
dp[i][i][j][j] = 0; // base case 1x1 rect
numr[i][j] += numr[i][j - 1] + numr[i - 1][j] - numr[i - 1][j - 1];
}
}
for (int ln = 0; ln < N; ln++) { // length on n side
for (int lm = 0; lm < M; lm++) {
for (int i = 1; i <= N; i++) {
if (i + ln > N) break;
for (int k = 1; k <= M; k++) {
if (k + lm > M) break;
int j = i + ln;
int l = k + lm;
int total = numr[j][l] - numr[j][k - 1] - numr[i - 1][l] + numr[i - 1][k - 1]; // total raisins in rect
for (int d = i; d < j; d++) { // divide along n side first
dp[i][j][k][l] = min(dp[i][j][k][l], total + dp[i][d][k][l] + dp[d+1][j][k][l]);
}
for (int d = k; d < l; d++) { // divide
dp[i][j][k][l] = min(dp[i][j][k][l], total + dp[i][j][k][d] + dp[i][j][d+1][l]);
}
}
}
}
}
cout << dp[1][N][1][M]; // ans is entire rectangle
}
