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;

typedef long long int ll;
const int INF = 1<<30;
const long long LINF = 1LL<<60;
const long long MOD = (long long)1e9 + 7;

int pop_count(long long bits){
    bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
    bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
    bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
    bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
    return (bits & 0x0000ffff) + (bits >>16 & 0x0000ffff);
}

struct segtree{
    int n;
    vector<int> d;
    function<int(int, int)> f;
    segtree(int mx){
        n = 1;
        while(n < mx) n <<= 1;
        d = vector<int>(n << 1);
    }
    int query(int a, int b, int i = 1, int l = 0, int r = -1){
        if(r == -1) r = n;
        if(a <= l && r <= b){
            return d[i];
        }
        int res = 0;
        int c = (l + r) >> 1;
        if(a < c) res |= query(a, b, i << 1, l, c);
        if(c < b) res |= query(a, b, i << 1 | 1, c, r);
        return res;
    }
    void update(int i, int x){
        i += n;
        d[i] = x;
        while(i){
            i >>= 1;
            d[i] = d[2 * i] | d[2 * i + 1];
        }
    }
    void set(int i, char c){
        d[i + n] = 1 << (c - 'a');
        update(i, d[i + n]);
    }
};

int main(){
    int n;
    string s;
    cin >> n >> s;
    segtree st(n);
    for(int i = 0; i < n; i++){
        st.set(i, s[i]);
    }
    int q;
    cin >> q;
    for(int i = 0; i < q; i++){
        int t;
        cin >> t;
        if(t == 1){
            int x;
            char c;
            cin >> x >> c;
            x--;
            st.set(x, c);
        }else{
            int x, y;
            cin >> x >> y;
            x--;
            cout << pop_count(st.query(x, y)) << endl;
        }
    }
    return 0;
}