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 <iostream>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <limits>
#include <string>
#include <bitset>
#include <functional>

using namespace std;
using lint = long long;
using pii = pair<int, int>;
using vec = vector<int>;
using pq = priority_queue<int>;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n); i > 0; i--)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define all(x) (x).begin(), (x).end()
#define foreach(it, x) for (auto it = (x).begin(); it != (x).end(); it++)
#define mp(x, y) make_pair((x), (y))
#define ctoi(x) (x) - 'a'
#define space " "

constexpr lint MOD = 1e9 + 7;
// int A, B, C, F, H, I, J, K, L, M, N, P, Q, S, T, U, W, X, Y;
// lint A, B, F, H, I, J, K, L, M, N, P, Q, S, T, U, W, X, Y;
// int ans = 0;
// string ans;
int N, Q, T, I, L, R;
string S;
char C;
map<char, set<int>> indexes;
vector<int> ans;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> N >> S >> Q;
	rep(i, N) {
		if (indexes.count(S[i]) == 0) {
			set<int> s = {i};
			indexes.insert(mp(S[i], s));
		} else {
			indexes[S[i]].insert(i);
		}
	}
	
	rep(i, Q) {
		cin >> T;

		if (T == 1) {
			cin >> I >> C;
			I--;
			indexes[S[I]].erase(I);
			if (indexes.count(C) == 0) {
				set<int> s = {I};
				indexes.insert(mp(C, s));
			} else {
				indexes[C].insert(I);
			}
		} else {
			cin >> L >> R;
			L--; R--;
			int rst = 0;
			for (char i = 'a'; i <= 'z'; i++) {
				if (indexes.count(i) == 0) continue;
				if (*indexes[i].lower_bound(L) <= R) {
                    if (indexes[i].lower_bound(L) == indexes[i].end()) {
                        continue;
                    }
					rst++;
				}
			}
			ans.push_back(rst);
		}
	}

	foreach(it, ans) {
		cout << *it << endl;
	}
	return 0;
}