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 (2.7.1) (judge verdict: Accepted)

z=[*$<]
m=1<<Math.log2(n=z[0].to_i).ceil
a=[0]*(m*2);
n.times{|i|c=z[1][i];a[i+=m]=1<<c.ord-97
a[i]=a[i*2]|a[i*2|1]while(i/=2)>0}
z[2].to_i.times{|k|t,l,r=z[3+k].split
i=l.to_i+m-1
if ?1==t
a[i]=1<<r.ord-97
a[i]=a[i*2]|a[i*2|1]while(i/=2)>0
else
j=r.to_i+m
x=0
((x|=a[i];i+=1)if i.odd?;x|=a[j-=1]if j.odd?;i/=2;j/=2)while i<j
p (0..25).sum{x[_1]}
end}