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 Julia (0.5.0) (judge verdict: Accepted)

type BIT
	n::Int
	bit::Array{Int}
	BIT(n)=new(n,zeros(Int,n))
end
function sum(bit::BIT,i::Int)
	ans=0
	while i>0
		ans+=bit.bit[i]
		i-=i&-i
	end
	ans
end
function add(bit::BIT,i::Int,a::Int)
	while i<=bit.n
		bit.bit[i]+=a
		i+=i&-i
	end
end
function main()
	N=parse(Int,readline())
	S=Char[]
	for c=chomp(readline())
		push!(S,c)
	end
	bits=[BIT(N) for _=1:26]
	for i=1:N
		x=Int(S[i])-96
		add(bits[x],i,1)
	end
	Q=parse(Int,readline())
	for _=1:Q
		qi,a,b=split(readline())
		if qi=="1"
			a=parse(Int,a)
			x=Int(S[a])-96
			add(bits[x],a,-1)
			S[a]=b[1]
			x=Int(S[a])-96
			add(bits[x],a,1)
		else
			a=parse(Int,a)
			b=parse(Int,b)
			cnt=0
			for i=1:26
				if sum(bits[i],b)>sum(bits[i],a-1)
					cnt+=1
				end
			end
			println(cnt)
		end
	end
end
main()