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 Python (3.4.3) (judge verdict: Time Limit Exceeded)

def main():
  import sys
  from numpy import zeros
  input=sys.stdin.buffer.readline
  n=int(input())+1
  data=zeros((n*2,26),int)
  def update(i,x):
    i+=n
    data[i]=0
    data[i,x]=1
    i//=2
    while i:
      data[i]=data[i*2]|data[i*2+1]
      i//=2
  def query(l,r):
    l+=n
    r+=n
    s=zeros(26,int)
    while l<r:
      if l&1:
        s|=data[l]
        l+=1
      if r&1:
        r-=1
        s|=data[r]
      l//=2
      r//=2
    return s.sum()
  for i,c in enumerate(input()[:-1],n):data[i,c-97]=1
  for i in range(n-1,0,-1):data[i]=data[i*2]|data[i-~i]
  s=[]
  for _ in range(int(input())):
    q,a,b=input().split()
    if q[0]>49:s+=query(int(a)-1,int(b)),
    else:update(int(a)-1,b[0]-97)
  print('\n'.join(map(str,s)))
main()