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

typedef struct _vertex{
  int label;
  struct _vertex *next;
}vertex;

void insert(vertex **L, int u, int v){
  vertex *t,*p = L[v],*new;
  t = L[v]->next;
  while(t != NULL){
    if(u > t->label){
      p = t;
      t = t->next;
    }
    else if(u == t->label)
      return;
    else
      break;
  }
  new = (vertex*)malloc(sizeof(vertex));
  new->label = u;
  new->next = t;
  if(L[v]->next == NULL)
    L[v]->next = new;
  else
    p->next = new;
  return;
}

int dfs(char *s ,vertex **L, int u, int *vis, int *back){
  int i;
  vertex *p;
  
  vis[u] = back[u] = 1;
  p = L[u]->next;
  while(p != NULL){
    if((!vis[p->label]) && dfs(s,L,p->label,vis,back))
	return 1;
    else if(back[p->label])
      return 1;
    p = p->next;
  }
  back[u] = 0;
  l += sprintf(s+l,"%d ",u);
  return 0;
}

/* int dfs(vertex **L, int u, int *vis){ */
/*   int i; */
/*   vertex *p; */
  
/*   vis[u] = 1; */
/*   p = L[u]->next; */
  
/*   while(p != NULL){ */
/*     if(!vis[p->label]) */
/*       if(dfs(L,p->label,vis)) */
/* 	return 1; */
/*     p = p->next; */
/*   } */
  
/*   printf("%d ", u); */
/*   return 0; */
/* } */

int main(){
  int n;
  printf("n = ");
  scanf("%d", &n);
  int u,v,i;
  vertex **L;
  vertex *t;
  
  L = (vertex**)malloc(n*sizeof(vertex*));
  for(i=0; i<n; i++){
    L[i] = (vertex*)malloc(sizeof(vertex));
    L[i]->label = i;
    L[i]->next = NULL;
  }
 
  printf("\nDependencies: ");
  while(1){
    scanf("%d", &u);
    if (u < 0)
      break;
    scanf("%d", &v);
    if(v < 0)
      break;
    insert(L,u,v);
  }

  for(i=0; i<n; i++){
    printf("%d: ",i);
    for(t = L[i]->next; t != NULL; t = t->next)
      printf("%d ",t->label);
    printf("\n");
  }

  int *vis = (int*)malloc(n*sizeof(int));
  int *back = (int*)malloc(n*sizeof(int));
  char s[1000] = "";
  
  for(i=0; i<n; i++)
    vis[i] = back[i] = 0;

  time = 0; l = 0;
  for(i=0; i<n; i++){
    if(!vis[i]){
      if(dfs(s,L,i,vis,back)){
	printf("There exists a cycle\n\n");
	return 1;
      }
    }
  }
  printf("%s\n\n",s);
  
  return 0;
}