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 $S_j \neq S_k$.
- $j - i \neq k - j$.

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

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

-----Output-----
Print the number of triplets in question.

-----Sample Input-----
4
RRGB

-----Sample Output-----
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.

见题面

见题面