Problem:
Score : 500 points

Problem Statement

You are given a string S of length N consisting of lowercase English letters.

Process Q queries of the following two types:

Type 1: change the i_q-th character of S to c_q. (Do nothing if the i_q-th character is already c_q.)

Type 2: answer the number of different characters occurring in the substring of S between the l_q-th and r_q-th characters (inclusive).

Constraints

N, Q, i_q, l_q, and r_q are integers.

S is a string consisting of lowercase English letters.

c_q is a lowercase English letter.

1 \leq N \leq 500000

1 \leq Q \leq 20000

|S| = N

1 \leq i_q \leq N

1 \leq l_q \leq r_q \leq N

There is at least one query of type 2 in each testcase.

Input

Input is given from Standard Input in the following format:

N
S
Q
Query_1
\vdots
Query_Q

Here, Query_i in the 4-th through (Q+3)-th lines is one of the following:

1 i_q c_q

2 l_q r_q

Output

For each query of type 2, print a line containing the answer.

Sample Input 1

7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7

Sample Output 1

3
1
5

In the first query, cdbb contains three kinds of letters: b , c , and d, so we print 3.

In the second query, S is modified to abcdzbd.

In the third query, a contains one kind of letter: a, so we print 1.

In the fourth query, S is modified to abcazbd.

In the fifth query, S does not change and is still abcazbd.

In the sixth query, abcazbd contains five kinds of letters: a, b, c, d, and z, so we print 5.

Solution in C++14 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <set>
#include <deque>
#include <utility>


int main(){
  int N, Q;
  scanf("%d", &N);
  std::string s;
  std::cin >> s;
  scanf("%d", &Q);
  std::vector<int > type(Q), l(Q), r(Q), I(Q);
  std::vector<char > c(Q);
  for (int i=0; i<Q; i++){
    //printf("i=%d\n", i);
    std::cin >> type[i];
    if (type[i]==1){
      std::cin >>  I[i] >> c[i];
      I[i]--;
    } else {
      std::cin >> l[i] >> r[i];
      l[i]--;
      r[i]--;
    }
  }

  std::set<int > pos[28];
  for (int i=0; i<N; i++){
    int val = int(s[i])-int('a');
    pos[val].insert(i);
  }
  
  /*for (int i=0; i<Q; i++){
    if (type[i]==1){
      int val = int(s[I[i]])-int('a');
      //printf("i=%d, s[i]=%c\n", I[i], s[I[i]]);
      auto itr = pos[val].find(I[i]);
      if (itr==pos[val].end()){
	printf("Error\n");
      }
      pos[val].erase(itr);
      val = int(c[i])-int('a');
      //printf("val=%d\n", val);
      pos[val].insert(I[i]);
      //s[I[i]]=c[i];
      //printf("end2\n");
      
    } else {
      int ans = 0;
      for (int j=0; j<26; j++){
	auto itr = std::lower_bound(pos[j].begin(), pos[j].end(), l[i]);
	//	printf("start1\n");
	if (itr!=pos[j].end() && *itr<=r[i]){
	  ans++;
	}
	//printf("end1\n");
      }
      std::cout << ans << std::endl;
    }
    }*/
  return 0;
}