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;
typedef pair<ll, ll> P;
const ll mod = 1e9+7;
const ll INF = 2e9;
const double PI = 3.1415926535;

char s[500001];
ll dat[2000000];
ll n;
int qa[20000];
void segtree_init(ll n_){
    n = 1; while(n < n_)n *= 2; //要素数を2のべき乗に
    for(int i = 0;i < 2 * n - 1;i++)dat[i] = 0;
}
void segtree_update(ll k, ll a){
    k += n-1; dat[k] = a;
    while(k > 0){
        k = (k-1)/2;
        dat[k] = dat[k*2+1] | dat[k*2+2];
    }
}
int query(int a, int b, int k, int l, int r){
    //[a, b)を知りたくていま[l, r)である節点kを見ている
    if(r <= a || b <= l)return 0; //求めたい範囲と被らない
    if(a <= l && r <= b)return dat[k]; //全て求めたい範囲に含まれている
    int vl = query(a, b, k*2+1, l, (l+r)/2);
    int vr = query(a, b, k*2+2, (l+r)/2, r);
    return vl | vr;
}

int main(void){
    ll n_; cin >> n_; cin >> s; ll q; cin >> q;
    segtree_init(n_);
    for(int i = 0;i < n_;i++){
        ll num = s[i] - 'a';
        num = 1 << num;
        segtree_update(i, num);
    }
    //for(int i = 0;i < n;i++)cout << dat[i] << endl;
    int ind = 0;
    for(int i = 0;i < q;i++){
        ll a; cin >> a;
        if(a == 1){
            ll b; char c; cin >> b >> c; b--;
            ll num = c - 'a';
            num = 1 << num;
            segtree_update(b, num);
        }else{
            ll b, c; cin >> b >> c; b--; c;
            int qu = query(b, c, 0, 0, n);
            int ans = 0;
            while(qu > 0){
                ans += qu % 2;
                qu /= 2;
            }
            qa[ind] = ans;
            ind++;
        }
    }
    for(int i = 0;i < ind;i++)cout << qa[i] << endl;
	return 0;
}