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 (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int int_min(int a,int b)
{
  if(a>=b){
    return b;
  }else{
    return a;
  }
}
void main(void)
{
  int N,r=0,g=0,b=0;
  //char *str;
  scanf("%d",&N);
  //str=(char*)malloc(sizeof(char)*N);
  char str[N+1];
  scanf("%s",str);
  for(int i=0;i<N;i++){
    //scanf("%c",&str[i]);
    if(str[i]=='R'){
      r++;
    }else if(str[i]=='G'){
      g++;
    }else if(str[i]=='B'){
      b++;
    }
  }
  int tmp=0;
  for(int i=1;i<=(N-2);i++){
    for(int j=1;j<=int_min(i,N-1-i);j++){
      if((str[i-j]!=str[i])&&(str[i-j]!=str[i+j])&&(str[i]!=str[i+j])){
        tmp++;
      }
    }
   }
                              
   printf("%d",r*g*b-tmp);


}