#include <iostream>
using namespace std;
int N, x;bool ok = true;int main(){ cin >> N; for(int i = 1; i <= N; i++) { cin >> x; if(i % 3 == 1 && x >= 0) ok = false; else if(i % 3 == 2 && x >= 0) ok = false; else if(i % 3 == 0 && x < 0) ok = false; } cout << ((ok == true)?"DA":"NO") << "\n"; return 0;}