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: Wrong Answer)

use std::collections::HashSet;


fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|i| i.parse().ok().unwrap())
        .collect()
}

fn main() {
    let _n = read::<usize>();
    let mut s = read::<String>();
    let mut cs = s.chars().collect::<Vec<char>>();

    let q = read::<usize>();
    for _ in 0..q {
        let data = read_vec::<String>();
        match &*data[0] {
            "1" => {
                let i: usize = data[1].parse().ok().unwrap();
                let c: char = data[2].parse::<String>().ok().unwrap()
                                    .chars().collect::<Vec<char>>()[0];
                s = cs.iter().enumerate().map(|(j, v)| {
                    if j == i - 1 {
                        return c;
                    } else {
                        return *v;
                    }
                }).collect::<String>();
            },
            "2" => {
                let l: usize = data[1].parse().ok().unwrap();
                let r: usize = data[2].parse().ok().unwrap();
                let mut hs: HashSet<char> = HashSet::new();
                for c in cs.iter().skip(l-1).take(r-l+1) {
                    hs.insert(*c);
                }
                println!("{}", hs.len());
            },
            _ => {}
        }
    }
}