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 PHP (7.4.4) (judge verdict: Wrong Answer)

<?php
list($n) = ints();
list($s) = strs();
for ($i = 0; $i < 26; ++$i) $cusum[chr(97 + $i)] = array_fill(0, $n + 1, 0);
for ($i = 0; $i < $n; ++$i) ++$cusum[$s[$i]][$i + 1];
for ($i = 0; $i < 26; ++$i)
    for ($j = 0; $j < $n; ++$j)
        $cusum[chr(97 + $i)][$j + 1] += $cusum[chr(97 + $i)][$j];
list($q) = ints();
for ($i = 0; $i < $q; ++$i) {
    list($type, $a, $b) = strs();
    if ($type === '1') {
        --$a;
        for ($j = $a + 1; $j <= $n; ++$j) {
            --$cusum[$s[$a]][$j];
            ++$cusum[$b][$j];
        }
    } else {
        --$a;
        --$b;
        $cnt = 0;
        for ($j = 0; $j < 26; ++$j)
            if ($cusum[chr(97 + $j)][$b + 1] - $cusum[chr(97 + $j)][$a]) ++$cnt;
        $output[] = $cnt;
    }
}
echo implode(PHP_EOL, $output);
function strs()
{
    return explode(' ', trim(fgets(STDIN)));
}
function ints()
{
    return array_map('intval', explode(' ', trim(fgets(STDIN))));
}