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 competitive::prelude::*;

type Value = u32;

#[derive(Debug)]
struct SegmentTree {
    data: Value,
    span: usize,
    l: Option<Box<SegmentTree>>,
    r: Option<Box<SegmentTree>>,
}

impl SegmentTree {
    fn new(s: &[char]) -> SegmentTree {
        if s.len() == 1 {
            SegmentTree {
                data: 1 << char2i(s[0]),
                span: 1,
                l: None,
                r: None,
            }
        } else {
            let m = s.len() / 2;
            let l = SegmentTree::new(&s[0..m]);
            let r = SegmentTree::new(&s[m..]);
            SegmentTree {
                data: l.data | r.data,
                span: s.len(),
                l: Some(Box::new(l)),
                r: Some(Box::new(r)),
            }
        }
    }

    fn update(&mut self, i: usize, c: char) {
        if self.span == 1 {
            assert!(self.l.is_none());
            assert!(self.r.is_none());
            assert!(i == 0);

            self.data = 1 << char2i(c);
        } else {
            let m = self.span / 2;
            let l = self.l.as_mut().unwrap();
            let r = self.r.as_mut().unwrap();
            if i < m {
                l.update(i, c);
            } else {
                r.update(i - m, c);
            }

            self.data = l.data | r.data;
        }
    }

    /// Query for [l, r)
    /// Pre-requirement: `l <= r` && `r <= self.span`
    fn query(&self, l: usize, r: usize) -> Value {
        assert!(l <= r);
        assert!(r <= self.span);

        if l == r {
            0
        } else if r - l == self.span {
            self.data
        } else {
            let m = self.span / 2;
            let ll = self.l.as_ref().unwrap();
            let rr = self.r.as_ref().unwrap();

            let lv = ll.query(min(l, m), min(r, m));
            let rv = rr.query(max(l, m) - m, max(m, r) - m);

            lv | rv
        }
    }
}

fn char2i(c: char) -> usize {
    assert!(c >= 'a' && c <= 'z');
    (c as u8 - 'a' as u8) as usize
}

fn main() {
    input! {
        _n: usize,
        s: Chars,
        qs: [(i32, Usize1, String)],
    }

    let mut st = SegmentTree::new(&s);

    for (qt, x, y) in qs {
        if qt == 1 {
            let i = x;
            let c = y.chars().nth(0).unwrap();
            st.update(i, c);
        } else if qt == 2 {
            let l = x;
            let r = y.parse::<usize>().unwrap() - 1;
            let ans = st.query(l, r + 1).count_ones();
            echo!(ans);
        } else {
            panic!("{}", qt);
        }
    }
}
*/

fn main() {
    let exe = "/tmp/binA638152D";
    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>";