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)

parseInt(x) = parse(Int, x)
parseMap(x::Array{SubString{String},1}) = map(parseInt, x)

function ftAdd(ft::Array{Int,1},k::Int,x::Int)
	t = k
	n = length(ft)
	while t<=n
		ft[t] += x
		t += t&(-t)
	end
	ft
end

function ftSum(ft::Array{Int,1},ll::Int,rr::Int)
	l = ll
	r = rr
	s = 0
	while r>0
		s += ft[r]
		r -= r&(-r)
	end
	while l>0
		s -= ft[l]
		l -= l&(-l)
	end
	s
end

function main()
	n = readline() |> parseInt
	s = readline() |> chomp
	t = [Int(s[i])-96 for i in 1:n]
	d = [zeros(Int,n) for i in 1:26]
	for i in 1:n
		ftAdd(d[t[i]],i,1)
	end
	q = readline() |> parseInt
	for iter in 1:q
		qr = readline() |> chomp |> split
		if qr[1][1]=='1'
			k = parseInt(qr[2])
			ftAdd(d[t[k]],k,-1)
			ftAdd(d[Int(qr[3][1])-96],k,1)
			t[k] = Int(qr[3][1])-96
		else
			l = parseInt(qr[2])-1
			r = parseInt(qr[3])
			f = 0
			for i in 1:26
				if ftSum(d[i],l,r)>0
					f += 1
				end
			end
			println(f)
		end
	end
end

main()