#include <bits/stdc++.h>
using namespace std;
const int N = 510;
char s[N][N], s1[N][N];
int n, k, l, r;
unsigned long long a[N];
set <pair<unsigned long long, int> > ss;
int main()
{
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
	{
		scanf("%s", s[i] + 1);
		memcpy(s1[i], s[i], sizeof s1[i]);
		sort(s[i] + 1, s[i] + 1 + n);
		for (int j = 1; j <= n; j++)
		{
			a[i] *= 127;
			a[i] += s[i][j];
		}
		ss.insert(make_pair(a[i], i));
	}
	for (auto i : ss)
	{
		auto it = ss.upper_bound(i);
		if (it == ss.end())
			break;
		if ((*it).first == i.first)
		{
			l = INT_MAX;
			r = 0;
			for (int j = 1; j <= n; j++)
				if (s1[i.second][j] != s1[(*it).second][j])
					l = min(l, j), r = max(r, j);
			if (r - l < k)
				return printf("DA"), 0;
		}
	}
	printf("NE");
	return 0;
}

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