This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#define ull unsigned long long
#define pll pair<ll, ll>
#define mp make_pair
#define ll long long
#define pb push_back
#define deb(x) cout << #x << " = " << x << endl
#define all(x) x.begin(), x.end()
#define ld long double
const ll mod1 = (ll)1e9 + 7;
const ll mod2 = (ll)1e9 + 9;
const ll BASE = 539;
const ll inf = (ll)1e18;
const long double e = 2.718281828459;
const long double pi = 3.141592653;
const ld EPS = 1e-9;
using namespace std;
template <class T>
istream& operator>>(istream &in, vector<T> &arr) {
    for (T &cnt : arr) {
        in >> cnt;
    }
    return in;
};
void solve() {
    ll n, k;
    cin >> n >> k;
    vector<string> arr(n);
    cin >> arr;
    vector<ll> p(27);
    p[0] = 1;
    for (int i = 1; i < 27; i++) {
        p[i] = (p[i - 1] * BASE) % mod1;
    }
    vector<ll> h(n);
    vector<vector<ll>> pref(n, vector<ll>(n + 1)), suff(n, vector<ll>(n + 1));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            pref[i][j + 1] = (pref[i][j] * BASE + arr[i][j] - 'a' + 1) % mod1;
            suff[i][n - j - 1] = (suff[i][n - j] * BASE + arr[i][n - j - 1] - 'a' + 1) % mod1;
        }
    }
    for (int i = 0; i < k; i++) {
        for (int j = 0; j < n; j++) {
            h[j] += p[arr[j][i] - 'a'];
            if (h[j] >= mod1) {
                h[j] -= mod1;
            }
        }
    }
    for (int i = k - 1; i < n; i++) {
        set<vector<ll>> used;
        for (int t = 0; t < n; t++) {
            vector<ll> cnt = {pref[t][i - k + 1], h[t], suff[t][i + 1]};
            if (used.count(cnt) != 0) {
                cout << "DA";
                return;
            }
            used.insert(cnt);
        }
        if (i + 1 < n) {
            for (int j = 0; j < n; j++) {
                h[j] -= p[arr[j][i - k + 1] - 'a'];
                if (h[j] < 0) {
                    h[j] += mod1;
                }
                h[j] += p[arr[j][i + 1] - 'a'];
                if (h[j] >= mod1) {
                    h[j] -= mod1;
                }
            }
        }
    }
    cout << "NE";
}
int main() {
#ifndef LOCAL
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
#else
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    cout.precision(30);
    ll seed = time(0);
    //cerr << "Seed: " << seed << "\n";
    srand(seed);
    solve();
    return 0;
}
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