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 <cstdio>
#include <cstring>
#include <cmath>
#include <utility>
#include <iostream>
#include <bitset>
#include <algorithm>
#include <vector>
#include <forward_list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#define rep(i, s, g) for ((i) = (s); (i) < (g); ++(i))
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
const ll MOD = 1e9 + 7;
const ll INF = (1ll << 60);

int n;
vector<bitset<26>> seg(1000010);
string s;

void update(int i, char x)
{
    seg[i + n][s[i] - 'a'] = 0;
    s[i] = x;
    seg[i + n][s[i] - 'a'] = 1;

    i += n;

    while (i > 0)
    {
        i = (i - 1) / 2;
        seg[i] = seg[2 * i + 1] | seg[2 * i + 2];
    }
}

bitset<26> query(int a, int b, int k, int l, int r)
{
    if (r <= a || b <= l)
    {
        bitset<26> bit(0ll);
        return bit;
    }

    if (a <= l && r <= b)
    {
        return seg[k];
    }
    else
    {
        bitset<26> bit1 = query(a, b, 2 * k + 1, l, (l + r) / 2);
        bitset<26> bit2 = query(a, b, 2 * k + 2, (l + r) / 2, r);

        return bit1 | bit2;
    }
}

int main(void)
{
    int q;
    int i, j;
    vector<int> ans;

    cin >> n >> s >> q;

    rep(i, 0, n)
    {
        update(i, s[i]);
    }

    rep(i, 0, q)
    {
        int x;

        cin >> x;

        if (x == 1)
        {
            int iq;
            char c;

            cin >> iq >> c;
            iq--;

            update(iq, c);
        }
        else
        {
            int l, r;
            int an = 0;

            cin >> l >> r;
            l--;

            bitset<26> bit = query(l, r, 0, -1, n);

            an = bit.count();

            ans.push_back(an);
        }
    }

    for (auto &z : ans)
    {
        cout << z << endl;
    }
}