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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input){
  input = input.split("\n");
  var N = parseInt(input[0],10);
  var S = input[1];
  var Q = parseInt(input[2],10);
  var nextInputnum = 3;
  var Querys = [];
  var S_arr = [];
  for(var i= 0; i < N;i++)S_arr.push(S[i]);
  for(var i = 0; i < Q ; i++)Querys[i] = input[(nextInputnum + i)];
  for(var qry of Querys){
    qry = qry.split(" ");
    var type = parseInt(qry[0],10);
    switch(type){
      case 1:
        var iq = parseInt(qry[1],10);
        var c = qry[2];
        if(S_arr[iq-1] !== c){
          S_arr[iq-1] = c;	
        }
        break;
      case 2:
        var l = parseInt(qry[1],10);
        var r = parseInt(qry[2],10);
        var result = {};
        if(l <= r && l < N){
          for(l; l <= r ;l++)result[S_arr[(l-1)]] = null;
        }
        var dup = Object.keys(result).length;
        console.log("%d\n",dup);
        break;
      default:
        break;
               }
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));