#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
vector<vi> grid;
vector<vi> sum;
vector<vi> sum0;
vector<vi> sum1;
int main() {
fast;
ll n,m;
cin in n in m;
ll cnt = 0;
fo(i,0,n+1){
vi a;
fo(j,0,m+1){
a.pb(0);
}
grid.pb(a);
sum.pb(a);
sum0.pb(a);
sum1.pb(a);
}
fo(i,1,n){
fo(j,1,m){
cin in grid[i][j];
if(!grid[i][j]) grid[i][j] = -1;
else cnt++;
sum0[i][j] = sum0[i-1][j]+sum0[i][j-1]-sum0[i-1][j-1]+(grid[i][j] == -1);
sum1[i][j] = sum1[i-1][j]+sum1[i][j-1]-sum1[i-1][j-1]+(grid[i][j] == 1);
sum[i][j] = sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1]+grid[i][j];
}
}
ll ans = INF;
fo(r1,1,n){
fo(r2,r1,n){
ll left = 1;
for(ll right = 1; right <= m;){
ll s = sum[r2][right]-sum[r2][left-1]-sum[r1-1][right]+sum[r1-1][left-1];
ll one = cnt-(sum1[r2][right]-sum1[r2][left-1]-sum1[r1-1][right]+sum1[r1-1][left-1]);
ll zero = sum0[r2][right]-sum0[r2][left-1]-sum0[r1-1][right]+sum0[r1-1][left-1];
mmin(ans,one+zero);
if(s < 0) left = right+1;
right++;
}
}
}
cout out ans;
return 0;
}
