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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc =new Scanner(System.in);
    int N=sc.nextInt();
    String S = sc.next();
    String s[] =S.split("",0);
    int t[] =new int[N];
    int x=0;int w=0;int a=0;int b=0; int c=0;
    for(int i=0;i<N;i++){
      if(s[i].equals("R")){t[i]=1;b=b+1;}
      else if(s[i].equals("G")){t[i]=2;a=a+1;}
      else{t[i]=3;c=c+1;}}
    for(int k=1;k<N-2;k++){
      int l=Math.min(k,N-k);
      for(int j=1;j<l;j++){
          if(t[k-j-1]+t[k-1]+t[k+j-1]==6){
            w=w+1;}}}
    int z=a*b*c;
    System.out.println(z-w);
  }
}