#include<bits/stdc++.h> using namespace std; #define rep(i,n) for(int i=0; i<(n); i++) #define rep2(i,a,b) for(int i=a; i<(b); i++) #define all(x) x.begin(),x.end() using ll=long long; const ll INF=1LL<<60; int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); ll n,m; cin>>n>>m; vector<vector<ll>> r(n+1,vector<ll>(m+1,0)); rep(i,n){ rep(j,m){ cin>>r[i+1][j+1]; r[i+1][j+1]+=r[i][j+1]+r[i+1][j]-r[i][j]; } } ll dp[51][51][51][51]; rep2(i,1,n+1){ rep(j,n){ ll lf=j,ri=j+i; if(ri>n)break; rep2(k,1,m+1){ rep(l,m){ ll up=l,dn=l+k; if(dn>m)break; dp[lf][ri][up][dn]=INF; ll raisin=r[ri][dn]+r[lf][up]-r[lf][dn]-r[ri][up]; if(i==1 and k==1){ dp[lf][ri][up][dn]=0; continue; } rep2(c,lf+1,ri){ dp[lf][ri][up][dn]=min(dp[lf][ri][up][dn],raisin+dp[lf][c][up][dn]+dp[c][ri][up][dn]); } rep2(c,up+1,dn){ dp[lf][ri][up][dn]=min(dp[lf][ri][up][dn],raisin+dp[lf][ri][up][c]+dp[lf][ri][c][dn]); } } } } } cout<<dp[0][n][0][m]<<"\n"; }