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: Wrong Answer)

#include<stdio.h>

char s[500000];

void type1(int i, char c){
	s[i] = c;
}

void type2(int l, int r){
	int m[50] = {0};
	int i, cnt = 0;
	int tmp;

	for(i=l-1; i < r; i++){
		tmp = (int)s[i]-'a';
		if(m[tmp] == 0){
			m[tmp] = 1;
			cnt++;
		}
	}

	printf("%d\n", cnt);
}

int main(){
	int n, q;
	int type;
	int l, r, i;
	char c;
	int j;

	scanf("%d", &n);
	scanf("%s", s);
	scanf("%d", &q);

	for(j=0; j<q; j++){
		scanf("%d", &type);
		if(type == 1){
			scanf("%d %c", &i, &c);
			type1(i, c);
		}else{
			scanf("%d %d", &l, &r);
			type2(l, r);
		}
	}

	return 0;
}