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: Accepted)

class IntSegmentTree(n: Int) {
    private var size = 1

    init {
        while (size < n) {
            size *= 2
        }
    }

    private val segTree = IntArray(size * 2 - 1) { 0 }

    fun update(x: Int, value: Int) {
        var tmp = x + size - 1

        segTree[tmp] = value
        while (tmp > 0) {
            tmp = (tmp - 1) / 2
            segTree[tmp] = segTree[2 * tmp + 1] + segTree[2 * tmp + 2]
        }
    }

    fun getSum(a: Int, b: Int, k: Int = 0, l: Int = 0, r: Int = size): Int {
        if (r <= a || b <= l) {
            return 0
        }
        if (a <= l && r <= b) {
            return segTree[k]
        }

        val vl = getSum(a, b, 2 * k + 1, l, (l + r) / 2)
        val vr = getSum(a, b, 2 * k + 2, (l + r) / 2, r)

        return vl + vr
    }
}

fun main(args: Array<String>) {
    val N = readInputLine().toInt()
    val S = readInputLine().toCharArray()
    val Q = readInputLine().toInt()

    val segTree = Array(26) { IntSegmentTree(N) }

    for (i in 0 until N) {
        segTree[S[i] - 'a'].update(i, 1)
    }

    for (i in 0 until Q) {
        val (q, p1, p2) = readInputLine().split(" ")
        if (q == "1") {
            val index = p1.toInt() - 1
            val ch = p2.first()

            segTree[S[index] - 'a'].update(index, 0)
            segTree[ch - 'a'].update(index, 1)
            S[index] = ch
        } else {
            val l = p1.toInt() - 1
            val r = p2.toInt() - 1

            var cnt = 0
            for (k in 0 until 26) {
                if (segTree[k].getSum(l, r + 1) != 0) {
                    cnt++
                }
            }

            println(cnt)
        }
    }
}

fun readInputLine(): String {
    return readLine()!!
}