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 Ruby (2.3.3) (judge verdict: Time Limit Exceeded)

I0 = "a".ord
bits = Array.new(26, 1 << 500000)

n = gets.to_i
s = gets.chomp.each_char.map { |c| c.ord - I0 }

flag = 1
s.each { |c| bits[c] |= flag; flag <<= 1 }

q = gets.to_i

q.times do
  type, a, b = gets.split

  if type == "1"
    i = a.to_i - 1
    b = b.ord - I0
    if bits[b][i] == 0
      c = s[i]
      s[i] = b
      flag = 1 << i
      bits[c] ^= flag
      bits[b] ^= flag
    end
  else
    mask = (1 << b.to_i) - (1 << a.to_i.pred)
    puts bits.count { |x| x & mask != 0 }
  end
end