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: Runtime Error)

#pragma GCC target("avx2")
#pragma GCC optimize("O3", "unroll-loops")

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

#define int long long

#define fastIO() ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define RANDOM() random_device __rd; \
                 mt19937 __gen = mt19937(__rd()); \
                 uniform_int_distribution<int> __dis(0, MAXN); \
                 auto rnd = bind(__dis, __gen);

const int MAXN = 1E6;
const int maxn = 1 << 19;

int BIT[26][maxn];

int lb(int x) {
    return x & -x;
}

void Add(int alpha, int idx, int val) {
    for (; idx < maxn; idx += lb(idx)) BIT[alpha][idx] += val;
}

int Sum(int alpha, int idxL, int idxR, int sum = 0) {
    --idxL;
    for (; idxR; idxR -= lb(idxR)) sum += BIT[alpha][idxR];
    for (; idxL; idxL -= lb(idxL)) sum -= BIT[alpha][idxL];
    return sum;
}

int32_t main() {
    fastIO();
    
    int n, q, op, idx, l, r, cnt;
    char c;
    string s;
    cin >> n >> s >> q;
    for (int i = 0; i < n; ++i) Add(s[i] - 'a', i + 1, 1);
    
    while (q--) {
        cin >> op;
        if (op == 1) {
            cin >> idx >> c;
            Add(s[idx] - 'a', idx + 1, -1);
            s[idx] = c;
            Add(s[idx] - 'a', idx + 1,  1);
        }
        else {
            cin >> l >> r, cnt = 0;
            for (int i = 0; i < 26; ++i) cnt += (Sum(i, l, r) > 0);
            cout << cnt << "\n";
        }
    }
    
    return 0;
}