Problem:
Score : 300 points

Problem Statement

You are given a string S of length N consisting of A, C, G and T. Answer the following Q queries:

Query i (1 \leq i \leq Q): You will be given integers l_i and r_i (1 \leq l_i < r_i \leq N). Consider the substring of S starting at index l_i and ending at index r_i (both inclusive). In this string, how many times does AC occurs as a substring?

Notes

A substring of a string T is a string obtained by removing zero or more characters from the beginning and the end of T.

For example, the substrings of ATCODER include TCO, AT, CODER, ATCODER and (the empty string), but not AC.

Constraints

2 \leq N \leq 10^5

1 \leq Q \leq 10^5

S is a string of length N.

Each character in S is A, C, G or T.

1 \leq l_i < r_i \leq N

Input

Input is given from Standard Input in the following format:

N Q
S
l_1 r_1
:
l_Q r_Q

Output

Print Q lines. The i-th line should contain the answer to the i-th query.

Sample Input 1

8 3
ACACTACG
3 7
2 3
1 8

Sample Output 1

2
0
3

Query 1: the substring of S starting at index 3 and ending at index 7 is ACTAC. In this string, AC occurs twice as a substring.

Query 2: the substring of S starting at index 2 and ending at index 3 is CA. In this string, AC occurs zero times as a substring.

Query 3: the substring of S starting at index 1 and ending at index 8 is ACACTACG. In this string, AC occurs three times as a substring.

Solution in Ruby (2.3.3) (judge verdict: Accepted)

# util functions

# debug
$debugFlag = ( ARGV[0] != nil )
p "==== DEBUG MODE ====" if $debugFlag

def pd(str)
  p str if $debugFlag
end

# input
inputs = []
lc = 0
while l = $stdin.gets do
  if lc == 1
    inputs << l.chomp
  else
    inputs << l.chomp.split(" ").map(&:to_i)
  end
  lc += 1
end

# input check
if $debugFlag
  p "--- INPUT (begin) ---"
  inputs.each do |l_i|
    p l_i
  end
  p "--- INPUT (end) ---"
  print "\n"
end

ss = inputs[1]
qs = inputs[2..-1]

# body
if $debugFlag
  p ss
  p qs
end

arr = []
idx = 0
sslen = ss.length
accnt = 0
while idx < sslen
  if ss[idx..idx+1] == "AC"
    accnt += 1    
    arr << accnt
    arr << accnt
    idx += 2
  else
    arr << accnt
    idx += 1
  end
end

pd ss
pd arr

qs.each do |s_j, e_j|
  chkarr = arr[s_j-1..e_j-1]
  if chkarr.size <= 1
    ret = 0
  else
    if ss[s_j-1..s_j] == "AC"
      min = chkarr[0]
    else
      min = chkarr[0] + 1
    end

    if chkarr[-2] == chkarr[-1]
      max = chkarr[-1]
    else
      max = chkarr[-1] - 1
    end
    
    if max < min
      ret = 0
    else
      ret = max - min + 1
    end
  end

  puts ret
end