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

struct Node {
  char *p;
  struct Node *next;
};

struct List {
  struct Node *head;
};

struct Node *cycleExist(struct List *list) {
  struct Node *iter1 = list->head;
  struct Node *iter2 = list->head;

  while (iter2 != NULL) {
    iter1 = iter1->next;
    iter2 = iter2->next;
    if (iter2 == NULL) {
      break;
    }
    iter2 = iter2->next;
    if (iter1 == iter2) {
      break;
    }
  }
  if (iter2 == NULL) {
    return NULL;
  }
  iter1 = list->head; // iter1指向头结点， iter2不动
  while (iter1 != iter2) {
    iter1 = iter1->next;
    iter2 = iter2->next;
  }
  return iter1;
}

int main() {
  int n;
  scanf("%d", &n);

  // 创建整个的结点数组或指针
  struct Node *node_arr = malloc(sizeof(struct Node) * n); // n 个结点
  for (int i = 0; i < n; i++) {
    struct Node *node = node_arr + i;
    node->p = malloc(21);
  }

  for (int sid = 1; sid <= n; sid++) {
    struct Node *snode = node_arr + sid - 1; // 取source node
    int tid;
    scanf("%s%d", snode->p, &tid);

    if (tid >=1 && tid <= n) {
      struct Node *tnode = node_arr + tid - 1; // 取target node
      snode->next = tnode;
    }
  }

  struct List list;
  list.head = node_arr;

  struct Node *node = cycleExist(&list);
  if (node) {
    printf("%s", node->p);
  } else {
    printf("-1");
  }

  for (int i = 0; i < n; i++) {
    struct Node *node = node_arr + i;
    free(node->p);
  }
  free(node_arr);
  return 0;
}