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>

#define rep(i, n) for(int i=0; i<n; i++)

#define N 500000
#define Q 20000

char S[N];

int count(char* start, char* end){
	char* pt;
	int letters[26] = {0};
	for(pt = start; pt < end; pt++){
		letters[*pt-'a']++;
	}
	
	int i;
	int count = 0;
	for(i=0; i<26; i++){
		if(letters[i]) count++;
	}
	
	return count;
}

int main(void){
	int dummy;//scanf return dummy
	
	int n;//not use
	dummy = scanf("%d", &n);//dummy input
	
	dummy = scanf("%s", S);
	
	int q;
	dummy = scanf("%d", &q);
	
	char type;
	char il;
	char cr;
	
	rep(i, q){
		dummy = scanf("%c %c %c", &type, &il, &cr);
		
		if(type == '1'){
			S[il-1] = cr;
		}else{
			printf("%d\n", count(&S[il-'0'], &S[cr-'0'+1]));
		}
	}
	
	return 0;
}