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)

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    (iter = $iter:ident, $($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut $iter = s.split_whitespace();
        input_inner!{$iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
    ($iter:expr, mut $var:ident $($r:tt)*) => {
        input_inner!{$iter, mut $var : usize $($r)*}
    };
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
    ($iter:expr, $var:ident $($r:tt)*) => {
        input_inner!{$iter, $var : usize $($r)*}
    };
}
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, { chars: $base:expr }) => {
        read_value!($iter, String).chars().map(|c| (c as u8 - $base as u8) as usize).collect::<Vec<usize>>()
    };
    ($iter:expr, { char: $base:expr }) => {
        read_value!($iter, { chars: $base })[0]
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, char) => {
        read_value!($iter, chars)[0]
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().unwrap()
    };
}
trait Monoid {
    type T: Clone + PartialEq;
    fn identity(&self) -> Self::T;
    fn binary_operate(&self, x: &Self::T, y: &Self::T) -> Self::T;
}
struct SegmentTree<M: Monoid> {
    n: usize,
    seg: Vec<M::T>,
    monoid: M,
}
impl<M: Monoid> SegmentTree<M> {
    fn from_vec(v: Vec<M::T>, monoid: M) -> SegmentTree<M> {
        let n = 1 << format!("{:b}", v.len() - 1).len();
        let mut seg = vec![monoid.identity(); 2 * n - 1];
        for (i, x) in v.into_iter().enumerate() {
            seg[i + n - 1] = x;
        }
        for i in (0..n - 1).rev() {
            seg[i] = monoid.binary_operate(&seg[2 * i + 1], &seg[2 * i + 2]);
        }
        SegmentTree {
            n: n,
            seg: seg,
            monoid: monoid,
        }
    }
    fn update(&mut self, k: usize, x: M::T) {
        let mut k = k + self.n - 1;
        self.seg[k] = x;
        while k > 0 {
            k = (k - 1) / 2;
            self.seg[k] = self
                .monoid
                .binary_operate(&self.seg[2 * k + 1], &self.seg[2 * k + 2]);
        }
    }
    fn query(&self, l: usize, r: usize) -> M::T {
        let mut l = l + self.n - 1;
        let mut r = r + self.n - 1;
        let mut res = self.monoid.identity();
        while l < r {
            if r & 1 == 0 {
                r -= 1;
                res = self.monoid.binary_operate(&res, &self.seg[r]);
            }
            if l & 1 == 0 {
                res = self.monoid.binary_operate(&res, &self.seg[l]);
                l += 1;
            }
            l = (l - 1) / 2;
            r = (r - 1) / 2;
        }
        res
    }
}
struct AnyMonoid<T: Clone, F: Fn(&T, &T) -> T> {
    id: T,
    op: F,
}
impl<T: Clone, F: Fn(&T, &T) -> T> AnyMonoid<T, F> {
    fn new(id: T, op: F) -> AnyMonoid<T, F> {
        AnyMonoid { id: id, op: op }
    }
}
impl<T: Clone + PartialEq, F: Fn(&T, &T) -> T> Monoid for AnyMonoid<T, F> {
    type T = T;
    fn identity(&self) -> T {
        self.id.clone()
    }
    fn binary_operate(&self, x: &T, y: &T) -> T {
        (self.op)(x, y)
    }
}
fn main() {
    input! { iter = iter, _n, s: {chars: 'a'}, q };
    let s = s.into_iter().map(|x| 1 << x).collect::<Vec<_>>();
    let mut seg = SegmentTree::from_vec(s, AnyMonoid::new(0u32, |&x, &y| x | y));
    for _i in 0..q {
        input_inner! { iter, x };
        if x == 1 {
            input_inner! { iter, i: usize1, c: {char: 'a'} };
            seg.update(i, 1 << c);
        } else {
            input_inner! { iter, l: usize1, r };
            println!("{}", seg.query(l, r).count_ones());
        }
    }
}