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

typedef struct cvor{
    int broj;
    struct cvor *l, *d;
}cvor;

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

    return novi;
}

cvor *formTree(int *niz, int n, int i)
{
    if(i >= n || niz[i] == -1) return NULL;
    cvor *koren = noviCvor(niz[i]);

    koren->l = formTree(niz, n, 2*i+1);
    koren->d = formTree(niz, n, 2*i+2);

    return koren;
}

void razmak(char c, int n)
{
    while(n--) putchar(c);
}
void vizuelniPrikaz(cvor *koren, int nivo)
{
    if(!koren)
    {
        razmak('\t', nivo);
        puts("~");
    }
    else
    {
        vizuelniPrikaz(koren->d, nivo+1);
        razmak('\t', nivo);
        printf("%d\n", koren->broj);
        vizuelniPrikaz(koren->l, nivo+1);
    }
}
int pruneInactiveServers(cvor *koren)
{
    if(!koren) return 0;

    int l = pruneInactiveServers(koren->l);
    int d = pruneInactiveServers(koren->d);

    if( !l ) koren -> l = NULL;
    if( !d ) koren -> d = NULL;
    
    return koren->broj + l + d;
}
int main()
{
    int i, n;
    scanf("%d", &n);

    int *niz = (int*)malloc(n * sizeof(int));

    for(i=0;i<n;i++)
    {
        scanf("%d", &niz[i]);
    }

    cvor *koren = formTree(niz, n, 0);

    vizuelniPrikaz(koren, 0);
    printf("==========\n");
    pruneInactiveServers(koren);
    vizuelniPrikaz(koren, 0);
    
    return 0;
}