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 alga::general::{AbstractGroup, AbstractMonoid, Additive, Operator};
use proconio::marker::{Bytes, Usize1};
use proconio::{fastout, input};

use std::marker::PhantomData;
use std::ops::{RangeInclusive, RangeTo, RangeToInclusive};

#[fastout]
fn main() {
    input! {
        n: usize,
        mut s: Bytes,
        queries: [Query],
    }

    let mut bits = vec![Bit::<_, Additive>::new(n); 27];

    macro_rules! bits(($c:expr) => (bits[usize::from($c - b'a')]));

    for (i, c) in s.iter().enumerate() {
        bits!(c).plus(i, &1);
    }

    for query in queries {
        match query {
            Query::_1((i, c)) => {
                bits!(s[i]).plus(i, &-1);
                bits!(c).plus(i, &1);
                s[i] = c;
            }
            Query::_2((l, r)) => {
                let ans = bits.iter().filter(|bits| bits.query(l..=r) > 0).count();
                println!("{}", ans);
            }
        }
    }
}

macro_rules! query {
    ($($var_name:ident: (<$var_ty:ty>, $head:literal, $read:expr)),+ $(,)?) => {
        enum Query {
            $($var_name($var_ty),)*
        }

        impl proconio::source::Readable for Query {
            type Output = Self;

            fn read<R: std::io::BufRead, S: proconio::source::Source<R>>(source: &mut S) -> Self {
                return match &*String::read(source) {
                    $($head => Self::$var_name(__apply($read, source)),)*
                    s => panic!("unexpected word {:?}", s),
                };

                fn __apply<T, O, F: FnOnce(T) -> O>(f: F, x: T) -> O {
                    f(x)
                }
            }
        }
    };
}

query! {
    _1: (<(usize, u8)>, "1", |s| (Usize1::read(s), char::read(s) as u8)),
    _2: (<(usize, usize)>, "2", |s| (Usize1::read(s), Usize1::read(s))),
}

#[derive(Clone, Debug)]
struct Bit<M, O> {
    nodes: Vec<M>,
    phantom: PhantomData<fn() -> O>,
}

impl<M: AbstractGroup<O>, O: Operator> Bit<M, O> {
    fn new(n: usize) -> Self {
        Self {
            nodes: vec![M::identity(); n],
            phantom: PhantomData,
        }
    }

    fn query<R: BitRange<M, O>>(&self, range: R) -> M {
        range.query(&self.nodes)
    }

    fn plus(&mut self, i: usize, x: &M) {
        let mut i_plus1 = i + 1;
        while i_plus1 <= self.nodes.len() {
            self.nodes[i_plus1 - 1] = self.nodes[i_plus1 - 1].operate(x);
            i_plus1 += 1 << i_plus1.trailing_zeros();
        }
    }
}

trait BitRange<M: AbstractMonoid<O>, O: Operator> {
    fn query(&self, nodes: &[M]) -> M;
}

impl<M: AbstractMonoid<O>, O: Operator> BitRange<M, O> for RangeTo<usize> {
    fn query(&self, nodes: &[M]) -> M {
        #[allow(clippy::range_minus_one)]
        match self.end {
            0 => M::identity(),
            end => (..=end - 1).query(nodes),
        }
    }
}

impl<M: AbstractMonoid<O>, O: Operator> BitRange<M, O> for RangeToInclusive<usize> {
    fn query(&self, nodes: &[M]) -> M {
        let mut acc = M::identity();
        let mut i_plus1 = self.end + 1;
        while i_plus1 > 0 {
            acc = acc.operate(&nodes[i_plus1 - 1]);
            i_plus1 -= 1 << i_plus1.trailing_zeros();
        }
        acc
    }
}

impl<M: AbstractGroup<O>, O: Operator> BitRange<M, O> for RangeInclusive<usize> {
    fn query(&self, nodes: &[M]) -> M {
        let l = (..*self.start()).query(nodes);
        let r = (..=*self.end()).query(nodes);
        r.operate(&l.two_sided_inverse())
    }
}
*/

fn main() {
    let exe = "/tmp/bin47B8A4F0";
    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>";