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:
/*
use fenwick::array::{prefix_sum, update};
use std::io;
use std::ops::{AddAssign, Sub};

#[derive(Copy, Clone, Default)]
struct CharInfo([i32; 26]);

impl AddAssign for CharInfo {
    fn add_assign(&mut self, rhs: CharInfo) {
        for i in 0..self.0.len() {
            self.0[i] += rhs.0[i];
        }
    }
}

impl Sub for CharInfo {
    type Output = CharInfo;
    fn sub(self, rhs: CharInfo) -> Self::Output {
        let mut out = CharInfo::default();
        for i in 0..self.0.len() {
            out.0[i] = self.0[i] - rhs.0[i];
        }
        out
    }
}

fn get<T: AddAssign + Sub<Output = T> + Copy + Default>(fenwick: &mut [T], i: usize) -> T {
    if i == 0 {
        prefix_sum(fenwick, 0)
    } else {
        prefix_sum(fenwick, i) - prefix_sum(fenwick, i - 1)
    }
}

fn main() {
    let stdin = io::stdin();
    let mut buf = String::new();
    stdin.read_line(&mut buf).unwrap();
    let n: usize = buf.trim_end().parse().unwrap();
    buf.clear();
    stdin.read_line(&mut buf).unwrap();
    let s = buf.trim_end().as_bytes().to_owned();
    buf.clear();
    stdin.read_line(&mut buf).unwrap();
    let q: usize = buf.trim_end().parse().unwrap();
    buf.clear();
    let queries: Vec<(usize, usize, String)> = (0..q)
        .map(|_| {
            buf.clear();
            stdin.read_line(&mut buf).unwrap();
            let mut split = buf.split_whitespace();
            (
                split.next().unwrap().parse().unwrap(),
                split.next().unwrap().parse().unwrap(),
                split.next().unwrap().to_owned(),
            )
        })
        .collect();
    let mut fenwick = vec![CharInfo::default(); n];
    for i in 0..n {
        let mut delta = CharInfo::default();
        delta.0[(s[i] - b'a') as usize] += 1;
        update(&mut fenwick, i, delta);
    }
    for query in queries {
        match query {
            (1, i, c) => {
                let c = c.as_bytes()[0];
                let cur = get(&mut fenwick, i - 1);
                let mut new = CharInfo::default();
                new.0[(c - b'a') as usize] += 1;
                update(&mut fenwick, i - 1, new - cur);
            }
            (2, l, r) => {
                let r: usize = r.parse().unwrap();
                let diff = if l == 1 {
                    prefix_sum(&mut fenwick, r - 1)
                } else {
                    prefix_sum(&mut fenwick, r - 1) - prefix_sum(&mut fenwick, l - 2)
                };
                println!("{}", diff.0.iter().filter(|&&x| x > 0).count());
            }
            _ => panic!(),
        }
    }
}
*/

fn main() {
    let exe = "/tmp/bin509AB5A2";
    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>";