#include <bits/stdc++.h>
#ifdef GUDEB
#define D(x) cerr << #x << ": " << (x) << '\n';
#define ifdeb if(true)
#else
#define D(x) ;
#define ifdeb if(false)
#endif
#define all(x) begin(x), end(x)
using namespace std;
using ull = unsigned long long;
using ll = long long;
// #define int ll;
int tb[50][50];
int tbps[51][51];
int optv[51][51][51][51];
int opth[51][51][51][51];
int val[51][51][51][51];
int gs(int uly, int ulx, int dry, int drx) {
return tbps[dry][drx]
- tbps[uly][drx]
- tbps[dry][ulx]
+ tbps[uly][ulx];
}
void solve() {
int n, m;
cin >> n >> m;
for(int i = 0; i < n; ++i) {
for(int j = 0; j < m; ++j) {
cin >> tb[i][j];
tbps[i+1][j+1] += tb[i][j];
tbps[i+1][j+1] += tbps[i+1][j];
tbps[i+1][j+1] += tbps[i][j+1];
tbps[i+1][j+1] -= tbps[i][j];
}
}
for(int i = 0; i < m; ++i) {
for(int j = i+1; j <= m; ++j) {
for(int k = 0; k < n; ++k) {
optv[k][k+1][i][j] = k+1;
}
}
}
for(int i = 0; i < n; ++i) {
for(int j = i+1; j <= n; ++j) {
for(int k = 0; k < m; ++k) {
opth[i][j][k][k+1] = k+1;
}
}
}
for(int vd = 1; vd <= n; ++vd) {
for(int hd = 1; hd <= m; ++hd) {
if(vd*hd == 1) continue;
for(int i = 0; i+vd <= n; ++i) {
for(int j = 0; j+hd <= m; ++j) {
D(i)
D(j)
D(vd)
D(hd)
int tv = gs(i,j,i+vd,j+hd);
int iv = 1 << 30;
//int opu = i+1;
//int opd = i+vd-1;
int opu = max(i+1, optv[i][i+vd-1][j][j+hd]);
int opd = min(i+vd-1, optv[i+1][i+vd][j][j+hd]);
D(opu)
D(opd)
for(int k = opu; k <= opd; ++k) {
int nv = val[i][k ][j][j+hd]
+ val[k][i+vd][j][j+hd];
if(iv > nv) {
iv = nv;
D(iv)
optv[i][i+vd][j][j+hd] = k;
}
}
int jv = 1 << 30;
//int opl = j+1;
//int opr = j+hd-1;
int opl = max(j+1, opth[i][i+vd][j][j+hd-1]);
int opr = min(j+hd-1, opth[i][i+vd][j+1][j+hd]);
D(opl)
D(opr)
for(int k = opl; k <= opr; ++k) {
int nv = val[i][i+vd][j][k]
+ val[i][i+vd][k][j+hd];
if(jv > nv) {
jv = nv;
D(jv)
opth[i][i+vd][j][j+hd] = k;
}
}
if(vd == 1) val[i][i+vd][j][j+hd] = tv + jv;
else if(hd == 1) val[i][i+vd][j][j+hd] = tv + iv;
else val[i][i+vd][j][j+hd] = tv + min(iv, jv);
}
}
}
}
cout << val[0][n][0][m] << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout << setprecision(20);
solve();
}
