#include <iostream>
using namespace std;

int main() {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    if (b % a != c % b != d % c || (b / a != c / b) ||
        (c / b != d / c)) {
        cout << "NU";
    } else {
        cout << "DA";
    }
    return 0;
}