#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001;
int N,M,g[5][5], ret = 100500;
vi cur;
void rotCol(int ind) {
char c = g[0][ind];
F0R(i,N-1) g[i][ind] = g[i+1][ind];
g[N-1][ind] = c;
}
void rotRow(int ind) {
char c = g[ind][0];
F0R(i,M-1) g[ind][i] = g[ind][i+1];
g[ind][M-1] = c;
}
bool checkRows() {
F0R(i,N) FOR(j,1,M) if (g[i][j] != g[i][0]) return 0;
return 1;
}
bool checkCols() {
F0R(j,M) FOR(i,1,N) if (g[i][j] != g[0][j]) return 0;
return 1;
}
void SEARCH(int ind, int ans) {
if (ind == N) {
if (checkCols() || checkRows()) ret = min(ret,ans);
return;
}
F0R(i,M) {
SEARCH(ind+1,ans+min(i,M-i));
rotRow(ind);
}
}
void search(int ind = 0, int ans = 0) {
if (ind == M) {
SEARCH(0,ans);
return;
}
F0R(i,N) {
search(ind+1,ans+min(i,N-i));
rotCol(ind);
}
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> N >> M; cur.resize(M);
F0R(i,N) F0R(j,M) cin >> g[i][j];
search();
cout << ret;
}
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( )
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/
