#include<stdio.h>
#include<conio.h>
#define N 15
int t[N],x[N],n,p,u;
void citire()
{FILE *f=fopen("euler.in","r");
 fscanf(f,"%d",&n);
 while(!feof(f))
 {p++;
  fscanf(f,"%d",&x[p]);
 }
 fclose(f); }
void st()
{int i;
 t[x[1]]=-1;u=1;
 for(i=2;i<=p;i++)
  if(t[i]) {if(x[i]==t[x[i-1]]) u=1;
		    else u=0;}
    else {if(u) {t[x[i]]=x[i-1];u=1;}
		 else u=0;}
}
void main()
{citire();
 st();
 if(u)
  {printf("DA\n");
   for(int i=1;i<=n;i++)
	if(t[i]!=-1)
	   printf("%d - %d \n",i,t[i]);
 }
  else printf("NU :((");
getch();}