#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
/*
Phu Trong from Nguyen Tat Thanh High School for gifted student
*/
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
int numRow, numCol, all = 0;
void process(void){
cin >> numRow >> numCol;
vector<vector<int>> A(numRow + 5, vector<int>(numCol + 5));
vector<vector<int>> pref(numRow + 5, vector<int>(numCol + 5));
FOR(i, 1, numRow) FOR(j, 1, numCol){
cin >> A[i][j];
all += A[i][j];
if(!A[i][j]) A[i][j] = -1;
}
FOR(j, 1, numCol) FOR(i, 1, numRow){
pref[i][j] = pref[i - 1][j] + A[i][j];
}
int res = 0;
FOR(l, 1, numRow) FOR(r, l, numRow){
int len = (r - l + 1);
int sum = 0;
for (int i = 1; i <= numCol; ++i){
sum += pref[r][i] - pref[l - 1][i];
maximize(res, sum);
if(sum < 0) sum = 0;
}
}
cout << all - res;
}
signed main(){
#define name "Whisper"
cin.tie(nullptr) -> sync_with_stdio(false);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
process();
return (0 ^ 0);
}
