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)

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

using ll = long long;

//constant
const double EPS = 1e-10;

#define REP(i, n) for (ll i = 0; i < n; i++)
#define FOR(i, s, e) for (ll i = s; i < e; i++)
#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(), (x).rend()

//debug
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define DEBUG(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl;

// view vector
template<typename T> void view(T e) { std::cout << e << std::endl; }
template<typename T> void view(const std::vector<T>& v) { for (const auto& e : v) { std::cout << e << " "; } std::cout << std::endl; }
template<typename T> void view(const std::vector<std::vector<T> >& vv) { for (const auto& v : vv) { view(v); } }

// DP
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }

// ***************************************

vector<set<ll>> num(26, set<ll>({1<<30}));
vector<char> S(5e5);

int cnt() {
	int l, r;
	cin >> l >> r; l--;

	int ret = 0;
	REP(i, 26) {
		if (num[i].empty()) continue;
		auto a = *num[i].lower_bound(l);
		auto b = *num[i].lower_bound(r);
		if (b > a) ret++;
	}

	return ret;
}

int main(){
	int N, Q;
	string tmp;
	cin >> N >> tmp >> Q;
	REP(i, N) {
		S[i] = tmp[i];
	}

	REP(i, N) {
		num[S[i] - 'a'].insert(i);
	}

	int q;
	REP(i, Q) {
		cin >> q;
		if (q == 1) {
			int idx;
			char c;
			cin >> idx >> c; idx--;
			if (S[idx] == c) continue;

			num[S[idx] - 'a'].erase(idx);
			num[c - 'a'].insert(idx);
			S[idx] = c;
		}
		else {
			cout << cnt() << endl;
		}
	}


	return 0;
}