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 PyPy3 (7.3.0) (judge verdict: Wrong Answer)

import random as r
class Skip_Node:
  def __init__(self,value):
    self.value=value
    self.height=1
    while r.random()<0.5:
      self.height+=1
    self.pointer=[None for i in range(self.height)]

class Skip_List:
  def __init__(self):
    self.max_height=1
    self.pointer=[None]
  
  def insert(self,value):
    node=Skip_Node(value)
    t=self.pointer[-1]
    bt=self
    for i in range(min(self.max_height,node.height)-1,-1,-1):
      while t!=None and t.value<value:
        bt,t=t,t.pointer[i]
      bt.pointer[i]=node
      node.pointer[i]=t
      t=bt
    for i in range(self.max_height,node.height):
      self.pointer.append(node)
  
  def find(self,value):
    t=self
    for i in range(self.max_height-1,-1,-1):
      while t.pointer[i]!=None and t.pointer[i].value<value:
        t=t.pointer[i]
    return t.pointer[0].value if t.pointer[0] else None
  
  def erase(self,value):
    t=self
    for i in range(self.max_height-1,-1,-1):
      while t.pointer[i]!=None and t.pointer[i].value<value:
        t=t.pointer[i]
      if t.pointer[i]!=None and t.pointer[i].value==value:
        t.pointer[i]=t.pointer[i].pointer[i]
    
n=int(input())
s=list(input())
ls=len(s)
toa="abcdefghijklmnopqrstuvwxyz"
ato={}
for i in range(26):
  ato[toa[i]]=i
l=[Skip_List() for i in range(26)]
for i in range(ls):
  l[ato[s[i]]].insert(i)

q=int(input())
for i in range(q):
  t,a,b=input().split()
  if t=="1":
    a=int(a)-1
    l[ato[s[a]]].erase(a)
    s[a]=b
    l[ato[b]].insert(a)
  else:
    c=0
    a=int(a)-1
    b=int(b)
    for i in range(26):
      f=l[i].find(a)
      if f!=None and f<b:
        c+=1
    print(c)