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: Accepted)

//g++ -std=c++14 test.cpp -o test.out
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <cassert>
#include <algorithm>
#include <functional>
#include <iostream>
#include <iomanip>
#include <vector>
#include <queue>
#include <map> 
#include <utility>
#include <limits.h>
#include <bitset>
#include <set>
using namespace std;
 
#define LL long long int
const LL INF = (LL)(1e18)+1;
const int INF_INT = 2147483647-1e6;
const LL mod = 1000000007ll;
const int mod_int = 1000000007;

int N;
string S;
int Q;

vector<int> ans;

void solve(){
	vector<set<int>> alpha_position(26);
	for(int s=0;s<N;s++){
		alpha_position[S[s]-'a'].insert(s);
	}
	for(int q=0;q<Q;q++){
		int query_type;cin >> query_type;
		if(query_type==1){
			int i;char c;cin >> i >> c;
			i--;
			alpha_position[S[i]-'a'].erase(i);
			alpha_position[c-'a'].insert(i);
			S[i] = c;
		}
		if(query_type==2){
			int l,r;cin >> l >> r;
			l--;r--;
			int counter = 0;
			for(int i='a';i<='z';i++){
				auto left = alpha_position[i-'a'].lower_bound(l);
				if(left==alpha_position[i-'a'].end()) continue;
				if((*left) <= r) counter++;
			}
			ans.push_back(counter);
		}
	}
}
 
int main(){
	cin >> N;
	cin >> S;
	cin >> Q;
 
	solve();

	for(int i=0;i<ans.size();i++)cout << ans[i] << endl;
	return 0;
}