#include<bits/stdc++.h>
using namespace std;
int N, M;
vector<vector<vector<vector<int>>>> DP;
//DP[x1][x2][y1][y2];
vector<vector<int>> preSum, raisinsMap;
int getSum(int x1, int x2, int y1, int y2){
int ans;
if(x1 <= 0){
if(y1 <= 0) ans = preSum[x2][y2];
else ans = preSum[x2][y2] - preSum[x2][y1-1];
}else{
if(y1 <= 0) ans = preSum[x2][y2]-preSum[x1-1][y2];
else{
ans = preSum[x2][y2] + preSum[x1-1][y1-1] - preSum[x2][y1-1] - preSum[x1-1][y2];
}
}
return ans;
}
int solve(int x1, int x2, int y1, int y2){
if(x1 == x2 && y1 == y2) return 0;
if(DP[x1][x2][y1][y2] != -1) return DP[x1][x2][y1][y2];
int payNow = getSum(x1, x2, y1, y2);
if(x1 == x2){
int ans = solve(x1, x2, y1+1, y2);
for(int dist = 1; (y1 + dist + 1) <= y2; ++dist){
ans = min(ans, solve(x1, x2, y1, y1+dist) + solve(x1, x2, y1+dist+1, y2));
}
//cout << "x from " << x1 << " to " << x2 << "\t y from " << y1 << " to " << y2 << "\t value paid " << ans << endl;
return DP[x1][x2][y1][y2] = payNow + ans;
}else if(y1 == y2){
int ans = solve(x1+1, x2, y1, y2);
for(int dist = 1; (x1 + dist + 1) <= x2; ++dist){
ans = min(ans, solve(x1, x1+dist, y1, y2) + solve(x1+dist+1, x2, y1, y2));
}
//cout << "x from " << x1 << " to " << x2 << "\t y from " << y1 << " to " << y2 << "\t value paid " << ans << endl;
return DP[x1][x2][y1][y2] = payNow + ans;
}else{
int ans = solve(x1, x2, y1, y1) + solve(x1, x2, y1+1, y2);
for(int dist = 1; (y1 + dist + 1) <= y2; ++dist){
ans = min(ans, solve(x1, x2, y1, y1+dist) + solve(x1, x2, y1+dist+1, y2));
}
for(int dist = 0; (x1 + dist + 1) <= x2; ++dist){
ans = min(ans, solve(x1, x1+dist, y1, y2) + solve(x1+dist+1, x2, y1, y2));
}
//cout << "x from " << x1 << " to " << x2 << "\t y from " << y1 << " to " << y2 << "\t value paid " << ans << endl;
return DP[x1][x2][y1][y2] = payNow + ans;
}
}
int main(){
cin >> N >> M;
raisinsMap = vector<vector<int>>(N, vector<int>(M));
preSum = vector<vector<int>>(N, vector<int>(M));
for(int i = 0; i < N; ++i){
for(int j = 0; j < M; ++j){
cin >> raisinsMap[i][j];
preSum[i][j] = raisinsMap[i][j];
if(i > 0 and j > 0){
preSum[i][j] += preSum[i-1][j] + preSum[i][j-1] - preSum[i-1][j-1];
}else{
if(i > 0) preSum[i][j] += preSum[i-1][j];
if(j > 0) preSum[i][j] += preSum[i][j-1];
}
//cout << preSum[i][j] << endl;
}
}
DP = vector<vector<vector<vector<int>>>>(N, vector<vector<vector<int>>>(N, vector<vector<int>>(M, vector<int>(M, -1))));
cout << solve(0, N-1, 0, M-1) << endl;
return 0;
}
