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)

fn read_stdin() -> String {
    use std::io::Read;
    let mut input = String::new();
    std::io::stdin().read_to_string(&mut input).unwrap();
    input
}

fn scan<'a, I: Iterator<Item = &'a str>, T: std::str::FromStr>(tokens: &mut I) -> T {
    tokens.next().unwrap().parse().ok().unwrap()
}

fn main() {
    let input = read_stdin();
    let tokens = &mut input.split_whitespace();
    let n: usize = scan(tokens);
    let bit: Vec<usize> = {
        let mut bit = vec![0; n];
        let mut b = 1;
        while b < n {
            let mut i = b;
            while i < n {
                bit[i] = b;
                i += 2 * b;
            }
            b *= 2;
        }
        bit
    };
    let s: String = scan(tokens);
    let mut s: Vec<usize> = s.bytes().map(|b| (b - b'a') as usize).collect();
    let mut count: Vec<Vec<usize>> = vec![vec![0; n]; 26];
    for mut i in 0..n {
        let c = s[i];
        while {
            count[c][i] += 1;
            i != 0
        } {
            i -= bit[i];
        }
    }
    let q: usize = scan(tokens);
    for _ in 0..q {
        let query_type: usize = scan(tokens);
        if query_type == 1 {
            let mut i: usize = scan(tokens);
            i -= 1;
            let c: String = scan(tokens);
            let c = (c.as_bytes()[0] - b'a') as usize;
            let d = s[i];
            s[i] = c;
            while {
                count[c][i] += 1;
                count[d][i] -= 1;
                i != 0
            } {
                i -= bit[i];
            }
        } else {
            let mut l: usize = scan(tokens);
            l -= 1;
            let mut cl = vec![0; 26];
            while l < n {
                for c in 0..26 {
                    cl[c] += count[c][l];
                }
                if l == 0 {
                    break;
                }
                l += bit[l];
            }
            let mut r: usize = scan(tokens);
            let mut cr = vec![0; 26];
            while r < n {
                for c in 0..26 {
                    cr[c] += count[c][r];
                }
                if r == 0 {
                    break;
                }
                r += bit[r];
            }
            let mut ans = 0;
            for c in 0..26 {
                if cl[c] > cr[c] {
                    ans += 1;
                }
            }
            println!("{}", ans);
        }
    }
}