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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php

fscanf(STDIN, "%d", $N);
fscanf(STDIN, "%s", $S);
fscanf(STDIN, "%d", $Q);

$new_text = [];
foreach(str_split($S) as $value){
    $new_text[] = 1 << (ord($value )- 97);
}

$ST = new SegmentTree($new_text);

while($Q--){

    fscanf(STDIN, "%d%d%s",$type, $from, $to);
    if($type === 1){

        $ST->update($from-1, (1 << (ord($to)-97)));

    }else{
        echo bitnum($ST->query($from-1, $to-1, 0, 0, $ST->size-1)).PHP_EOL;

    }

}



class SegmentTree{

    /**
     * @var array
     */
    private $tree = [];
    public $size = 0;
    private $default = 0;

    function __construct($array, $default=0){
        $count = count($array);
        $pow = floor(log($count, 2));
        $pow = (int)pow(2,$pow);
        while($count>$pow){
            $pow*=2;
        }
        $this->size = $pow;
        $this->tree = array_merge(array_fill(0,$pow-1,$default), $array, array_fill(0, $pow-$count, $default));
        $this->default = $default;
//        for($i=$this->size - intdiv($this->size,2)-1; $i < $this->size-1;$i++){
//            $this->updateUP($i);
//        }
        $this->updateAll();
    }

    function update($target, $value){
        $target = $target + $this->size -1;
        $this->tree[$target] = $value;
        $this->updateUP(intdiv($target-1, 2));

    }

    function updateUP($target){

//      while($target >=0){
//          $this->tree[$target] = $this->ev($this->tree[($target << 1) + 1], $this->tree[($target <<1) + 2]);
//          $target-=1;
//          $target>>=1;
//      }

        if($target != 0){
            $this->updateUP(($target-1)>>1);
        }
    }

    function updateAll(){
        for($i = $this->size-2;$i>=0;$i--){
            $this->tree[$i] = $this->ev($this->tree[$i * 2 + 1], $this->tree[$i * 2 + 2]);
        }
    }

    function query($from, $to, $node, $node_from, $node_to){

        if($node_from > $to || $node_to < $from){
            return $this->default;
        }
        if($node_to <= $to && $node_from >= $from){
            return $this->tree[$node];
        }else{
            $left = $this->query($from, $to, 2*$node + 1, $node_from, intdiv($node_from + $node_to, 2));
            $right = $this->query($from, $to, 2*$node + 2, intdiv($node_from + $node_to, 2)+1, $node_to);
            return $this->ev($left,$right);
        }


    }

    function ev($new, $comp){
        return $new | $comp;
    }

}
function bitnum($bits){
    $bits = ($bits & 0x55555555) + ($bits >> 1 & 0x55555555);
    $bits = ($bits & 0x33333333) + ($bits >> 2 & 0x33333333);
    $bits = ($bits & 0x0f0f0f0f) + ($bits >> 4 & 0x0f0f0f0f);
    $bits = ($bits & 0x00ff00ff) + ($bits >> 8 & 0x00ff00ff);
    return ($bits & 0x0000ffff) + ($bits >>16 & 0x0000ffff);
}