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C - GeT AC

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.

8 3
ACACTACG
3 7
2 3
1 8

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.