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)

use std::collections::{HashMap, HashSet};
use std::io::{stdin, Read};

macro_rules! parse {
    ($it: ident) => {
        $it.next().unwrap().parse().unwrap()
    };
    ($it: ident,2) => {
        (parse!($it), parse!($it))
    };
    ($it: ident,3) => {
        (parse!($it), parse!($it), parse!($it))
    };
    ($it: ident,4) => {
        (parse!($it), parse!($it), parse!($it), parse!($it))
    };
    ($it: ident, $n: ident) => {
        (&mut $it).take($n).map(|e| e.parse().unwrap()).collect();
    };
}
trait Monoid {
    fn unit() -> Self;
    fn add(lhs: Self, rhs: Self) -> Self;
}

struct SegTree<T: Monoid + Clone> {
    dat: Vec<T>,
    n: usize,
}

impl<T: Monoid + Copy> SegTree<T> {
    pub fn new(n: usize) -> Self {
        let dat = vec![T::unit(); n << 1];
        SegTree { dat: dat, n: n }
    }
    pub fn update(&mut self, k: usize, v: T) {
        let mut k = k + self.n;
        self.dat[k] = v;
        while {
            k >>= 1;
            k > 0
        } {
            self.dat[k] = T::add(self.dat[k << 1], self.dat[k << 1 | 1]);
        }
    }
    pub fn get(&self, a: usize, b: usize) -> T {
        let mut a = a + self.n;
        let mut b = b + self.n;
        let mut va = T::unit();
        let mut vb = T::unit();
        while a < b {
            if a & 1 != 0 {
                va = T::add(va, self.dat[a]);
                a += 1;
            }
            if b & 1 != 0 {
                vb = T::add(self.dat[b - 1], vb);
            }
            a >>= 1;
            b >>= 1;
        }
        T::add(va, vb)
    }
}

impl Monoid for usize {
    fn unit() -> usize {
        return 0;
    }
    fn add(lhs: Self, rhs: Self) -> Self {
        lhs | rhs
    }
}

fn main() {
    let mut s = String::new();
    stdin().read_to_string(&mut s).unwrap();
    let mut it = s.split_whitespace();
    let n: usize = parse!(it);
    let s = it.next().unwrap();
    let q: usize = parse!(it);
    let mut seg = SegTree::<usize>::new(n);
    for (i, b) in s.bytes().enumerate() {
        seg.update(i, 1 << (b - b'a'));
    }
    for _ in 0..q {
        let t: usize = parse!(it);
        if t == 1 {
            let i: usize = parse!(it);
            let i = i - 1;
            let cq = it.next().unwrap().bytes().next().unwrap();
            seg.update(i, 1 << (cq - b'a'));
        } else {
            let (l, r): (usize, usize) = parse!(it, 2);
            let c = seg.get(l - 1, r);
            println!("{}", c.count_ones());
        }
    }
}