#include <bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long int
#define tc ll test;cin >> test;while(test--)
#define vi vector<ll>
#define pll pair<ll,ll>
#define pb push_back
#define mp make_pair
#define INF 1e18
#define MOD 1000000007
#define ff first
#define ss second
#define in >>
#define out <<
#define space << " " <<
#define spacef << " "
#define fo(i,a,b) for(ll i = a; i <= b; i++)
#define rfo(i,a,b) for(ll i = a; i >= b; i--)
#define nextline out "\n"
#define print(x) for(auto i : x ) cout out i spacef
#define mmax(x,i) x = max(x,i)
#define mmin(x,i) x = min(x,i)
#define N 105
int main() {
fast;
ll n,m;
cin in n in m;
vector<vi> grid(n+5,vi(m+5));
vector<vi> sum0(n+5,vi(m+5));
vector<vi> sum1(n+5,vi(m+5));
ll cnt1 = 0;
fo(i,1,n){
fo(j,1,m){
cin in grid[i][j];
if(grid[i][j]) cnt1++;
sum0[i][j] = sum0[i][j-1]+sum0[i-1][j]-sum0[i-1][j-1] + (grid[i][j] == 0);
sum1[i][j] = sum1[i][j-1]+sum1[i-1][j]-sum1[i-1][j-1] + grid[i][j];
}
}
ll ans = INF;
fo(i1,1,n){
fo(j1,1,m){
fo(i2,i1,n){
fo(j2,j1,m){
ll zero = sum0[i2][j2]-sum0[i2][j1-1]-sum0[i1-1][j2]+sum0[i1-1][j1-1];
ll one = cnt1-(sum1[i2][j2]-sum1[i2][j1-1]-sum1[i1-1][j2]+sum1[i1-1][j1-1]);
mmin(ans,zero+one);
}
}
}
}
cout out ans;
return 0;
}
