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 Rust (1.15.1) (judge verdict: Accepted)

// This code is generated by [cargo-atcoder](https://github.com/tanakh/cargo-atcoder)
// Original source code:
/*
#[allow(unused_imports)]
use itertools::Itertools as _;
use proconio::input;
#[allow(unused_imports)]
use procontools::p;
#[allow(unused_imports)]
use std::cmp::*;

#[derive(Debug)]
pub struct SegmentTree<T, F> {
    pub data: Vec<T>,
    f: F,
    size: usize,
    ident: T, // f(x, ident) = f(ident, x) = x for all x in T
}
impl<T, F> SegmentTree<T, F>
where
    T: Clone + Copy,
    F: Fn(T, T) -> T,
{
    pub fn from(vec: &Vec<T>, f: F, ident: T) -> Self {
        let size = vec.len().next_power_of_two();
        let mut data = vec![ident; 2 * size];
        for i in 0..vec.len() {
            data[size + i] = vec[i];
        }
        for i in (1..size).rev() {
            data[i] = f(data[2 * i], data[2 * i + 1]);
        }
        Self {
            data,
            f,
            size,
            ident,
        }
    }
    pub fn update(&mut self, index: usize, value: T) {
        let mut x = index + self.size;
        let f = &self.f;
        self.data[x] = value;
        while x > 0 {
            x = x / 2;
            self.data[x] = f(self.data[2 * x], self.data[2 * x + 1]);
        }
    }
    pub fn get(&self, l: usize, r: usize) -> T {
        let (mut sl, mut sr) = (self.ident, self.ident);
        let f = &self.f;
        #[allow(non_snake_case)]
        let (mut L, mut R) = (l + self.size, r + self.size);
        while L < R {
            if L & 1 == 1 {
                sl = f(sl, self.data[L]);
                L += 1;
            }
            if R & 1 == 1 {
                R -= 1;
                sr = f(self.data[R], sr);
            }
            L >>= 1;
            R >>= 1;
        }
        f(sl, sr)
    }
}
impl<T, F> std::ops::Index<usize> for SegmentTree<T, F> {
    type Output = T;
    fn index(&self, index: usize) -> &Self::Output {
        &self.data[index + self.size]
    }
}

use proconio::marker::Chars;

fn main() {
    input! {
    n:usize,s:Chars,q:usize,qu:[(usize,usize,String);q]
    };
    let s = s
        .into_iter()
        .map(|c| 1 << (c as u32 - 'a' as u32))
        .collect_vec();
    let mut st = SegmentTree::from(&s, |a, b| a | b, 0u32);
    for q in qu {
        if q.0 == 1 {
            st.update(
                q.1 as usize-1,
                1 << (q.2.chars().next().unwrap() as u32 - 'a' as u32),
            );
        } else {
            let a: u32 = st.get(q.1 - 1, q.2.parse::<usize>().unwrap());
            p!(a.count_ones());
        }
    }
}
*/

fn main() {
    let exe = "/tmp/binFB2BC15D";
    std::io::Write::write_all(&mut std::fs::File::create(exe).unwrap(), &decode(BIN)).unwrap();
    std::fs::set_permissions(exe, std::os::unix::fs::PermissionsExt::from_mode(0o755)).unwrap();
    std::process::exit(std::process::Command::new(exe).status().unwrap().code().unwrap())
}

fn decode(v: &str) -> Vec<u8> {
    let mut ret = vec![];
    let mut buf = 0;
    let mut tbl = vec![64; 256];
    for i in 0..64 { tbl[TBL[i] as usize] = i as u8; }
    for (i, c) in v.bytes().filter_map(|c| { let c = tbl[c as usize]; if c < 64 { Some(c) } else { None } }).enumerate() {
        match i % 4 {
            0 => buf = c << 2,
            1 => { ret.push(buf | c >> 4); buf = c << 4; }
            2 => { ret.push(buf | c >> 2); buf = c << 6; }
            3 => ret.push(buf | c),
            _ => unreachable!(),
        }
    }
    ret
}

const TBL: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const BIN: &'static str = "<base64-encoded ELF executable removed>";