Problem Statement

We have a string S of length N consisting of R, G, and B.
Find the number of triples (i,~j,~k)~$(1 \leq i < j < k \leq N)$ that satisfy both of the following conditions:

• $S_i \neq S_j, S_i \neq S_k$, and $S_j \neq S_k$.
• $j - i \neq k - j$.

Input

Input is given from Standard Input in the following format:
N
S

Output

Print the number of triplets in question.

Constraints

• $1 \leq N \leq 4000$
• S is a string of length N consisting of R, G, and B.

Sample Input 1

4
RRGB

Sample Output 1

1

Only the triplet (1,~3,~4) satisfies both conditions. The triplet (2,~3,~4) satisfies the first condition but not the second, so it does not count.

Sample Input 2

39
RBRBGRBGGBBRRGBBRRRBGGBRBGBRBGBRBBBGBBB

Sample Output 2

1800

见题面 Input 部分

见题面 Output 部分