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 C (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int count(char *str, int start, int end) {
    int flag[26];
    for (int i = 0; i < 26; i++) {
        flag[i] = 0;
    }

    for (int i = start - 1; i < end; i++) {
        // printf("%c\n", str[i]);
        // printf("%d\n", (int) str[i] - 97);
        flag[(int) str[i] - 97] = 1;
    }

    int result = 0;
    for (int i = 0; i < 26; i++) {
        result += flag[i];
    }

    return result;
}

int main(void) {
    int length;
    scanf("%d", &length);
    char str[length];
    scanf(" %s", str);

    long int query_num;
    scanf(" %ld", &query_num);
    for (int i = 0; i < query_num; i++) {
        int type;
        scanf(" %d", &type);
        if (type == 1) {
            int num;
            char c;
            scanf(" %d %c", &num, &c);
            str[num - 1] = c;
            // printf("%s\n", str);
        } else if (type == 2) {
            int start, end;
            scanf(" %d %d", &start, &end);
            printf("%d\n", count(str, start, end));
        }
    }
    return 0;
}