#include <stdio.h>
#include <stdlib.h>

typedef struct cvor
{
    int br;
    struct cvor *l, *d;
    int balans;
} cvor;

cvor *noviCvor( int x )
{
    cvor *novi = ( cvor * ) malloc( sizeof( cvor ) );
    novi -> br = x;
    novi -> l = novi -> d = NULL;
    novi -> balans = 0;

    return novi;
}

int max( int x, int y )
{
    return x > y ? x : y;
}

int dubina( cvor *t )
{
    if( !t ) return 0;
    return 1 + max( dubina( t -> l ), dubina( t -> d ) );
}

void lRotacija( cvor **t )
{
    cvor *poml = *t;
    cvor *pomd = poml -> d;
    poml -> d = pomd -> l;
    pomd -> l = poml;
    *t = pomd;

    poml -> balans = dubina( poml -> d ) - dubina( poml -> l );
    pomd -> balans = dubina( pomd -> d ) - dubina( pomd -> l );
}

void dRotacija( cvor **t )
{
    cvor *pomd = *t;
    cvor *poml = pomd -> l;
    pomd -> l = poml -> d;
    poml -> d = pomd;
    *t = poml;

    poml -> balans = dubina( poml -> d ) - dubina( poml -> l );
    pomd -> balans = dubina( pomd -> d ) - dubina( pomd -> l );
}

int dodaj( cvor **koren, int x )
{
    cvor *t = *koren;

    if( !t )
    {
        t = noviCvor( x );
        *koren = t;
        return 1;
    }
    
    int inc;
    if( x > t -> br ) inc = dodaj( &t -> d, x );
    else inc = -dodaj( &t -> l, x );

    t -> balans += inc;

    if( inc && t -> balans )
    {
        if( t -> balans < -1 )
            if( t -> l -> balans < 0 ) dRotacija( &t );
            else
            {
                lRotacija( &t -> l );
                dRotacija( &t );
            }
        else if( t -> balans > 1 )
            if( t -> d -> balans > 0 ) lRotacija( &t );
            else
            {
                dRotacija( &t -> d );
                lRotacija( &t );
            }
        else return 1;
    }

    *koren = t;
    return 0;
}

cvor *unos()
{
    cvor *koren = NULL;

    int x;
    scanf("%d", &x );
    while( x )
    {
        dodaj( &koren, x );
        scanf("%d", &x );
    }

    return koren;
}

void razmak( int n )
{
    for( int i = 0; i < n; i ++ ) putchar('\t');
}

void vizuelniPrikaz( cvor *koren, int nivo )
{
    if( !koren )
    {
        razmak( nivo );
        puts("~");
    }
    else
    {
        vizuelniPrikaz( koren -> d, nivo + 1 );
        razmak( nivo );
        printf("%d\n", koren -> br );
        vizuelniPrikaz( koren -> l, nivo + 1 );
    }
}

int brCvorova( cvor *koren, int *nijeIdealno )
{
    if( *nijeIdealno ) return -1;
    if( !koren ) return 0;

    int l = brCvorova( koren -> l, nijeIdealno );
    int d = brCvorova( koren -> d, nijeIdealno );

    if( l == d ) return 1 + 2*l;
    *nijeIdealno = 1;

    return -1;
}

int daLiJeStabloIdealno( cvor *koren )
{
    int nijeIdealno = 0;
    brCvorova( koren, &nijeIdealno );

    if( nijeIdealno ) return 0;
    return 1;
}

int main()
{
    cvor *koren = unos();

    vizuelniPrikaz( koren, 0 );

    if( daLiJeStabloIdealno( koren ) ) printf("DA\n");
    else printf("NE\n");

    return 0;
}