tata

#include <iostream>
#define Nmax 100001
using namespace std;
int n,t[Nmax],v[Nmax];

void dfs(int k)
{
	v[k]=1;
	for(int i=1;i<=n;++i)
		if(t[i]==k)
			dfs(i);
}

int main()
{
    cin>>n;
    int rad=0;
    for(int i=1;i<=n;++i)
    {
        cin>>t[i];
        if(t[i]==0)
            rad=i;
    }
    if(rad==0)
        cout<<"NU";
    else
    {
        dfs(rad);
        for(int i=1;i<=n;++i)
            if(v[i]==0)
            {
                cout<<"NU";
                return 0;
            }
        cout<<"DA";
    }
    return 0;
}