#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int litmax = 26;
const int nmax = 20;

struct Trie {
  char lit;
  int pref;
  Trie* son[litmax];
};


Trie* root;

void addtrie(Trie* node, char* s) {
  node->pref++;
  if(*s != '\0') {
    int pos = (*s - 'a');
    if(node->son[pos] == NULL) {
      node->son[pos] = new Trie();
      node->son[pos]->lit = *s;
    }
    addtrie(node->son[pos], s + 1);
  }
}

void deltrie(Trie* node, char* s) {
  node->pref--;
  if(*s != '\0') {
    int pos = (*s - 'a');
    deltrie(node->son[pos], s + 1);
  }
}

int aparitii(Trie* node, char* s) {
  if(*s == '\0') {
    int prefsons = 0;
    for(int i=0; i < litmax; i++)
      if(node->son[i] != NULL)
        prefsons += node->son[i]->pref;
    return (node->pref - prefsons);
  } else {
    int pos = (*s - 'a');
    if(node->son[pos] == NULL)
        return 0;
    return aparitii(node->son[pos], s + 1);
  }
}

int prefix(Trie* node, char* s, int lung = 0) {
  if(*s == '\0') {
    if(node->pref == 0)
      return -1;
    else
      return lung;
  } else {
    int pos = (*s - 'a');
    if(node->son[pos] == NULL) {
      if(node->pref == 0)
        return -1;
      else
        return lung;
    } else {
      return max(prefix(node->son[pos], s + 1, lung + 1), node->pref != 0 ? lung : -1);
    }
  }
}

int main() {
  freopen("trie.in", "r", stdin);
  freopen("trie.out", "w", stdout);

  root = new Trie();
  root->lit = '@';
  root->pref = 0;

  int n;
  while(scanf("%d", &n) != EOF) {
    char s[nmax + 3];
    scanf("%s", s);
    if(n == 0) {
      addtrie(root, s);
    } else if(n == 1) {
      deltrie(root, s);
    } else if(n == 2) {
      printf("%d\n", aparitii(root, s));
    } else {
	 printf("%d\n", prefix(root, s));
    }
  }

  return 0;
}