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++ (GCC 9.2.1) (judge verdict: Runtime Error)

#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int,int>;

class SegTree{
    int _size;
    vector<int> _data;
public:
    SegTree(int size){
        _size = 1; while(_size < size) _size *= 2;
        _data.resize(size * 2);
    }

    void add(int i, int v){
        i += (_size - 1);
        _data[i] = v;
        while(i > 0){
            i = (i - 1) / 2;
            _data[i] = _data[i*2+1] | _data[i*2+2];
        }
    }

    int get(int a, int b, int now=0, int l=0, int r=-1){
        if(r < 0) r = _size;
        if(l >= b || r <= a) return 0;
        if(a <= l && r <= b) return _data[now];
        int vl = get(a, b, now*2+1, l, (l+r)/2);
        int vr = get(a, b, now*2+2, (l+r)/2, r);
        return vl | vr;
    }
};

int main(){
    int N;cin >> N;
    string S;cin >> S;
    int Q; cin >> Q;
    SegTree segt(N);
    rep(i, N){
        int x = S[i] - 'a';
        segt.add(i, (1<<x));
    }
    rep(i, Q){
        char x, l, r; cin >> x >> l >> r;
        if(x == '1'){
            int x = r - 'a';
            segt.add(l-'1', (1<<x));
        }else{
            int x = segt.get(l-'0'-1, r-'0');
            int ans = 0;
            rep(i, 26){
                if(x>>i&1) ans++;
            }
            cout << ans << endl;
        }
    }
    return 0;
}