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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
  ll n, q;
  string s;
  cin >> n;
  cin >> s;
  cin >> q;

  map<char, set<ll>> m;
  for (ll i = 0; i < (ll) s.size(); i++) {
    m[s[i]].insert(i + 1);
  }

  for (ll i = 0; i < q; i++) {
    int num;
    cin >> num;
    if (num == 1) {
      ll iq;
      char cq;
      cin >> iq >> cq;
      m[s[iq - 1]].erase(iq);
      m[cq].insert(iq);
    } else {
      ll lq, rq;
      cin >> lq >> rq;

      ll ans = 0;
      for (char c = 'a'; c <= 'z'; c++) {
        auto it = m[c].lower_bound(lq);
        if (it == m[c].end()) continue;
        if (*it <= rq) ans++;
      }
      cout << ans << endl;
    }
  }
}