//author: Ahmet Alp Orakci #include <bits/stdc++.h> using namespace std; using i64 = long long; const int MAXN = 1E3 + 5; char matrix[MAXN][MAXN]; #define ONLINE_JUDGE void solve() { memset(matrix, 'x', sizeof(matrix)); int n, k; cin >> n >> k; for(int i = 1; i <= n; i++) { for(int j = 1; j <= n; j++) { cin >> matrix[i][j]; } } auto reversex = [&](int x) -> void { for(int i = 1; i <= n; i++) { matrix[x][i] = (matrix[x][i] == 'o' ? 'x' : 'o'); } }; for(int i = 1; i <= n -1; i++) { if(matrix[i][1] != matrix[i +1][1]) { reversex(i +1); } } bool ans = true; for(int i = 1; i <= n -1; i++) { for(int j = 1; j <= n; j++) { ans &= matrix[i][j] == matrix[i +1][j]; } } cout << (ans ? "DA" : "NE"); return; } signed main() { #ifndef ONLINE_JUDGE freopen(".in", "r", stdin); freopen(".out", "w", stdout); #endif ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); int t = 1; //cin >> t; for(int i = 1; i <= t; i++) { solve(); } return 0; }