codeforces#P1168B. Good Triple
Good Triple
Description
Toad Rash has a binary string $s$. A binary string consists only of zeros and ones.
Let $n$ be the length of $s$.
Rash needs to find the number of such pairs of integers $l$, $r$ that $1 \leq l \leq r \leq n$ and there is at least one pair of integers $x$, $k$ such that $1 \leq x, k \leq n$, $l \leq x < x + 2k \leq r$, and $s_x = s_{x+k} = s_{x+2k}$.
Find this number of pairs for Rash.
The first line contains the string $s$ ($1 \leq |s| \leq 300\,000$), consisting of zeros and ones.
Output one integer: the number of such pairs of integers $l$, $r$ that $1 \leq l \leq r \leq n$ and there is at least one pair of integers $x$, $k$ such that $1 \leq x, k \leq n$, $l \leq x < x + 2k \leq r$, and $s_x = s_{x+k} = s_{x+2k}$.
Input
The first line contains the string $s$ ($1 \leq |s| \leq 300\,000$), consisting of zeros and ones.
Output
Output one integer: the number of such pairs of integers $l$, $r$ that $1 \leq l \leq r \leq n$ and there is at least one pair of integers $x$, $k$ such that $1 \leq x, k \leq n$, $l \leq x < x + 2k \leq r$, and $s_x = s_{x+k} = s_{x+2k}$.
Samples
010101
3
11001100
0
Note
In the first example, there are three $l$, $r$ pairs we need to count: $1$, $6$; $2$, $6$; and $1$, $5$.
In the second example, there are no values $x$, $k$ for the initial string, so the answer is $0$.