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 JavaScript (Node.js 12.16.1) (judge verdict: Runtime Error)

'use strict'
const Main=input=>{
    input=input.split("\n");
    const num=parseInt(input[0]);
    const str=input[1];
    
    const count=0;
    
    for(let i=1;i<num+1;i++){
        for(let j=i+1;j<num+1;j++){
            for(let k=j+1;k<num+1;k++){
                if(k-j!=j-i){
                    if(str[i]!=str[j]||str[i]!=str[k]||str[j]!=str[k]){
                        count++;
                    }
                }
            }
        }
    }
    
    console.log(count);
}

Main(require("fs").readFileSync("/dev/stdin","utf8"));