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: Time Limit Exceeded)

<?php
$n = intval(fgets(STDIN));
$str = trim(fgets(STDIN));
$Q = intval(fgets(STDIN));

$seg = new SegTree($n);
function op($a, $b){return $a | $b;}

for($i = 0; $i < $n; $i++){
  $seg->set($i, 1<<(ord($str[$i])-97));
}
while($Q--){
  list($q, $a, $b) = explode(" ", trim(fgets(STDIN)));
  if($q == "1"){
    $seg->set($a-1, 1<<(ord($b)-97));
  }else{
    echo popcount($seg->get($a-1, $b)), "\n";
  }
}


class SegTree{
  public $tree;
  public $bits;
  function __construct($n){
    $this->bits = max(1, ceil(log($n)/log(2)));
    for($i = 0; $i < $this->bits; ++$i){
      $this->tree[$i] = array_fill(0, 2**($this->bits-$i), 0);
    }
  }
  function set($i, $amount){
    $this->tree[0][$i] = $amount;
    for($j = 1; $j < $this->bits; ++$j){
      $this->tree[$j][$i>>$j] = op($this->tree[$j-1][$i>>$j<<1], $this->tree[$j-1][($i>>$j<<1) + 1]);
    }
  }
  function get($f, $t){
    $sum = 0;
    for($i = 1; $i <= $this->bits ; ++$i){
      $ff = $f>>$i<<$i;
      if($f!=$ff){
        $sum = op($sum, $this->tree[$i-1][$f>>($i-1)]);
        $f+=1<<($i-1);
      }
      $tt = $t>>$i<<$i;
      if($t!=$tt){
        $sum = op($sum, $this->tree[$i-1][($t>>($i-1))-1]);
        $t-=1<<($i-1);
      }
      if($f==$t)break;
    }
    return $sum;
  }
}

function o(...$val){
    if(count($val)==1)$val = array_shift($val);
    $trace = debug_backtrace();
    echo $trace[0]['line'].")";
    if(is_array($val)){
        if(count($val) == 0){
            echo "empty array";
        }elseif(!is_array(current($val))){
            echo "array: ";
            echo implode(" ", addIndex($val))."\n";
        }else{
            echo "array:array\n";
            if(isCleanArray($val)){
                foreach($val as $row)echo implode(" ", addIndex($row))."\n";
            }else{
                foreach($val as $i => $row)echo "[".$i."] ".implode(" ", addIndex($row))."\n";
            }
        }
    }else{
        echo $val."\n";
    }
}
function addIndex($val){
    if(!isCleanArray($val)){
        $val = array_map(function($k, $v){return $k.":".$v;}, array_keys($val), $val);
    }
    return $val;
}
function isCleanArray($array){
    $clean = true;
    $i = 0;
    foreach($array as $k => $v){
        if($k != $i++)$clean = false;
    }
    return $clean;
}
//ビットカウント-1の数を数える
function popcount($x){
    $con = 0;
    while ($x) {
        $x &= $x-1;
        ++$con;
    }
    return $con;
}