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++ (GCC 9.2.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stdio.h>
#include<cstring>
#include<math.h>
#include<map>
#include<bitset>
#include<iomanip>
#include<queue>
#include<functional>
#include<stack>
#include<tuple>
#include<cassert>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
using ll = long long;
using P = pair<int, int>;
using MATRIX = vector< vector<ll> >;
template <class T> inline bool chmin(T &x, const T &y) {if (x > y) {x = y; return 1;} return 0;}
template <class T> inline bool chmax(T &x, const T &y) {if (x < y) {x = y; return 1;} return 0;}

int N;
string S;
int Q;
const int INF = 1000000000;

int main() {
  cin >> N >> S >> Q;
  multiset<int> s[26];

  rep(i, N) {
    s[S[i]-'a'].insert(i);
  }
  rep(j, 26) {
    s[j].insert(INF);
  }
  vector<int> ans;
  rep(i, Q) {
    int temp;
    cin >> temp;
    if(temp == 1) {
      int j;
      char c;
      cin >> j >> c;
      j--;
      s[S[j]-'a'].erase(j);
      S[j] = c;
      s[S[j]-'a'].insert(j);
    } else {
      int l, r;
      cin >> l >> r;
      l--;r--;
      int t = 0;
      rep(j, 26) {
        if(s[j].empty()) continue;
        int p = *s[j].lower_bound(l);
        if(p <= r) {
          t++;
        }
      }
      ans.push_back(t);
    }
  }
  rep(i, ans.size()) {
      cout << ans[i] << endl;
  }
  return 0;
}