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 Go (1.6) (judge verdict: Runtime Error)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var ts [][]int
var sz int

func main() {
	var n int
	fmt.Scan(&n)
	var sc = bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	bs := []byte(sc.Text())

	sc.Scan()
	q, _ := strconv.Atoi(sc.Text())

	sz = 1
	for sz < n {
		sz *= 2
	}
	ts = make([][]int, 26)
	for j := range ts {
		ts[j] = make([]int, sz*2-1)
		for i := 0; i < n; i++ {
			var x int
			if int(bs[i]-'a') == j {
				x = 1
			}
			ts[j][i+sz-1] = x
		}
		for i := sz - 2; i >= 0; i-- {
			ts[j][i] = max(ts[j][2*i+1], ts[j][2*i+2])
		}
	}

	for i := 0; i < q; i++ {
		sc.Scan()
		a, _ := strconv.Atoi(sc.Text())
		if a == 1 {
			sc.Scan()
			b, _ := strconv.Atoi(sc.Text())
			sc.Scan()
			c := []byte(sc.Text())[0]
			b--
			if c != bs[b] {
				update(int(bs[b]-'a'), b, 0)
				update(int(c-'a'), b, 1)
			}
		} else {
			sc.Scan()
			b, _ := strconv.Atoi(sc.Text())
			sc.Scan()
			c, _ := strconv.Atoi(sc.Text())
			b--
			var sum int
			for j := 0; j < 26; j++ {
				sum += get(j, b, c, 0, 0, -1)
			}
			fmt.Println(sum)
		}
	}
}

func update(j, x, val int) {
	x += (sz - 1)
	ts[j][x] = val
	for x > 0 {
		x = (x - 1) / 2
		ts[j][x] = max(ts[j][2*x+1], ts[j][2*x+2])
	}
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func get(j, a, b, k, l, r int) int {
	if r < 0 {
		r = sz
	}
	if r <= a || b <= l {
		return 0
	}
	if a <= l && r <= b {
		return ts[j][k]
	}
	vl := get(j, a, b, 2*k+1, l, (l+r)/2)
	vr := get(j, a, b, 2*k+2, (l+r)/2, r)
	return max(vl, vr)
}