#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e18;
ll N, M;
ll memo[51][51][51][51];
vector<vector<ll> > grid;
vector<vector<ll> > pfxSum;
ll dp(ll top, ll bottom, ll left, ll right) {
assert(top <= bottom && left <= right);
if (top == bottom && left == right) return 0;
if (memo[top][bottom][left][right] != -1) {
return memo[top][bottom][left][right];
}
ll currCost = pfxSum[bottom][right] - pfxSum[top - 1][right] - pfxSum[bottom][left - 1] + pfxSum[top - 1][left - 1];
ll minForHori = INF, minForVert = INF;
if (left != right) {
for (ll endLeft = left; endLeft < right; endLeft++) {
minForHori = min(minForHori, dp(top, bottom, left, endLeft) + dp(top, bottom, endLeft + 1, right));
}
}
if (top != bottom) {
for (ll endTop = top; endTop < bottom; endTop++) {
minForVert = min(minForVert, dp(top, endTop, left, right) + dp(endTop + 1, bottom, left, right));
}
}
return memo[top][bottom][left][right] = currCost + min(minForHori, minForVert);
}
int main() {
cin.tie(0);
ios_base::sync_with_stdio(false);
memset(memo, -1LL, sizeof(memo));
cin >> N >> M;
grid.resize(N + 1, vector<ll>(M + 1, 0));
for (ll i = 1; i <= N; i++) {
for (ll j = 1; j <= M; j++) {
cin >> grid[i][j];
}
}
pfxSum.resize(N + 1, vector<ll>(M + 1, 0));
for (ll i = 1; i <= N; i++) {
for (ll j = 1; j <= M; j++) {
pfxSum[i][j] = pfxSum[i - 1][j] + pfxSum[i][j - 1] - pfxSum[i - 1][j - 1] + grid[i][j];
}
}
cout << dp(1, N, 1, M) << endl;
}
