Problem:
Score : 400 points

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.

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 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

Solution in C (Clang 10.0.0) (judge verdict: Wrong Answer)

#include<stdio.h>

int main(void) 
{
	int N;
	scanf("%d\n",& N);
	char S[N+1];
	scanf("%s", S);
	int i,j,r=0,b=0,g=0;
	for (i = 0; i < N; i++) {
		if (S[i] == 'R') r++;
		else if (S[i] == 'B') b++;
		else if(S[i]=='G')g++;
	}
	long int x=0;
	for (j = 0; j+j < N ; j++) {
		for(i = 0; i + j + j < N; i++) {
			if (S[i] != S[i + j] && S[i + j] != S[i + j + j] && S[i + j + j] != S[i])
				x++;
		}
	}
	printf("%ld", r * b * g - x);

	return 0;
}