#include <iostream>
using namespace std;
int verificare (int sir [ ],int n)
{
for (int i=0;i <n-1;i++)
{
if (v [i]>v [i+1]) return 0;
}
return 1;
}
int main ()
{
int n;
cin>>n;
int v [n];
for (int i=0;i <n;i++)
{
cin>>v [i];
}
if (verificare (v,n)) cout <<"Da";
else cout <<"NU";
return 0;
}
