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 Kotlin (1.0.0) (judge verdict: Time Limit Exceeded)

import java.util.*

fun main(args: Array<String>) {
    val pw = java.io.PrintWriter(System.out)
    Problem.solve(Scanner(System.`in`), pw)
    pw.flush()
}

class SortedList<A : Comparable<A>>(a: Collection<A>) : Iterable<A> {
    private val list = a.sorted()
    override fun iterator(): Iterator<A> = list.iterator()

    fun lowerBoundIndex(target: A): Int {
        var l = -1
        var r = list.count()
        while (l + 1 < r) {
            val mid = (l + r) / 2
            if (list[mid] >= target) r = mid
            else l = mid
        }
        return r
    }

    fun lowerBound(target: A): Iterator<A> = list.listIterator(lowerBoundIndex(target))
}

fun <A : Comparable<A>> Collection<A>.toSortedList() = SortedList(this)

object Problem {
    fun solve(sc: Scanner, pw: java.io.PrintWriter) {
        val N = sc.next().toInt()
        val S = sc.next().map { it - 'a' }.toIntArray()
        val Q = sc.next().toInt()

        val alphaIndexes = Array(26) { sortedSetOf<Int>() }
        for (i in 0 until N) {
            alphaIndexes[S[i]].add(i)
        }

        repeat(Q) {
            when (sc.next()) {
                "1" -> {
                    val i = sc.next().toInt() - 1
                    val c = sc.next().toCharArray().first() - 'a'
                    alphaIndexes[S[i]].remove(i)
                    S[i] = c
                    alphaIndexes[c].add(i)
                }
                "2" -> {
                    val l = sc.next().toInt() - 1
                    val r = sc.next().toInt() - 1
                    var ans = 0
                    alphaIndexes.forEach { indexes ->
                        val min = indexes.toSortedList().lowerBound(l)
                        if (min.hasNext() && min.next() <= r) {
                            ans++
                        }
                    }
                    pw.println(ans)
                }
            }
        }
    }
}