Buggy python submission (verdict: Time Limit Exceeded):
# coding: utf-8
# Your code here!
#from sys import stdin
#import math
#from functools import reduce
    
#A, B, C = [int(x) for x in stdin.readline().rstrip().split()]
N = int(input())
S = input()
 
counter = 0
 
for k in range(N):
    sk = S[k]
    for j in range(1,k):
        s = 'RGB'
        sj = S[j]
        if (sk == sj):continue
        s = s.replace(sk, '')
        s = s.replace(sj, '')
        diff = k-j
        if j-diff < 0:
            buf = S[0:j]
        #print(j-diff+1,j+1,k+1)
        #print(S)
        #print(S[0:j-diff], S[j-diff+1:j])
        else:
            buf = S[0:j-diff] + S[j-diff+1:j]
        counter = counter + buf.count(s)
        #print(s, buf.count(s), counter)
 
print(counter)

Fixed submission:
N = int(input())

S = input()

ans = 0


sumR = [0]
sumG = [0]
sumB = [0]

for s in S:
    if s == "R":
        sumR.append(sumR[-1] + 1)
        sumG.append(sumG[-1])
        sumB.append(sumB[-1])
    elif s == "G":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1] + 1)
        sumB.append(sumB[-1])
    elif s == "B":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1])
        sumB.append(sumB[-1] + 1)


for i, s in enumerate(S):
    not_cnt = 0
    for k in range(1, min(i + 1, N - i)):
        L, R = S[i - k], S[i + k]
        if s != L and s != R and L != R:
            not_cnt += 1

    cnt = 0
    if s == "R":
        cnt += sumG[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumG[-1] - sumG[i + 1])
    elif s == "G":
        cnt += sumR[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumR[-1] - sumR[i + 1])
    elif s == "B":
        cnt += sumG[i] * (sumR[-1] - sumR[i + 1])
        cnt += sumR[i] * (sumG[-1] - sumG[i + 1])

    cnt -= not_cnt
    ans += cnt


print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
# coding: utf-8
# Your code here!
#from sys import stdin
#import math
#from functools import reduce
    
#A, B, C = [int(x) for x in stdin.readline().rstrip().split()]
N = int(input())
S = input()
 
counter = 0
 
for k in range(N):
    sk = S[k]
    for j in range(k):
        sj = S[j]
        #print(sk, sj)
        if (sk == sj):
            continue
        for i in range(j):
            if (j-i)==(k-j):
                continue
            si = S[i]
            if (si==sj):
                continue
            elif (si==sk):
                continue
            else:
                counter = counter + 1
 
print(counter)

Fixed submission:
N = int(input())

S = input()

ans = 0


sumR = [0]
sumG = [0]
sumB = [0]

for s in S:
    if s == "R":
        sumR.append(sumR[-1] + 1)
        sumG.append(sumG[-1])
        sumB.append(sumB[-1])
    elif s == "G":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1] + 1)
        sumB.append(sumB[-1])
    elif s == "B":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1])
        sumB.append(sumB[-1] + 1)


for i, s in enumerate(S):
    not_cnt = 0
    for k in range(1, min(i + 1, N - i)):
        L, R = S[i - k], S[i + k]
        if s != L and s != R and L != R:
            not_cnt += 1

    cnt = 0
    if s == "R":
        cnt += sumG[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumG[-1] - sumG[i + 1])
    elif s == "G":
        cnt += sumR[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumR[-1] - sumR[i + 1])
    elif s == "B":
        cnt += sumG[i] * (sumR[-1] - sumR[i + 1])
        cnt += sumR[i] * (sumG[-1] - sumG[i + 1])

    cnt -= not_cnt
    ans += cnt


print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
# coding: utf-8
# Your code here!
#from sys import stdin
#import math
#from functools import reduce
    
#A, B, C = [int(x) for x in stdin.readline().rstrip().split()]
N = int(input())
S = input()
 
counter = 0
 
for k in range(N):
    for j in range(k):
        for i in range(j):
            if (j-i)==(k-j):
                continue
            si = S[i]
            sj = S[j]
            sk = S[k]
            if (si==sj):
                continue
            elif (si==sk):
                continue
            elif (sj==sk):
                continue
            counter = counter + 1
 
print(counter)

Fixed submission:
N = int(input())

S = input()

ans = 0


sumR = [0]
sumG = [0]
sumB = [0]

for s in S:
    if s == "R":
        sumR.append(sumR[-1] + 1)
        sumG.append(sumG[-1])
        sumB.append(sumB[-1])
    elif s == "G":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1] + 1)
        sumB.append(sumB[-1])
    elif s == "B":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1])
        sumB.append(sumB[-1] + 1)


for i, s in enumerate(S):
    not_cnt = 0
    for k in range(1, min(i + 1, N - i)):
        L, R = S[i - k], S[i + k]
        if s != L and s != R and L != R:
            not_cnt += 1

    cnt = 0
    if s == "R":
        cnt += sumG[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumG[-1] - sumG[i + 1])
    elif s == "G":
        cnt += sumR[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumR[-1] - sumR[i + 1])
    elif s == "B":
        cnt += sumG[i] * (sumR[-1] - sumR[i + 1])
        cnt += sumR[i] * (sumG[-1] - sumG[i + 1])

    cnt -= not_cnt
    ans += cnt


print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
# coding: utf-8
# Your code here!
from sys import stdin
import math
#from functools import reduce
    
#A, B, C = [int(x) for x in stdin.readline().rstrip().split()]
N = int(input())
S = input()

counter = 0

for k in range(N):
    for j in range(k):
        for i in range(j):
            if (j-i)==(k-j):
                continue
            if (S[i]!=S[j])&((S[i]!=S[k]))&((S[j]!=S[k])):
                counter = counter + 1

print(counter)

Fixed submission:
N = int(input())

S = input()

ans = 0


sumR = [0]
sumG = [0]
sumB = [0]

for s in S:
    if s == "R":
        sumR.append(sumR[-1] + 1)
        sumG.append(sumG[-1])
        sumB.append(sumB[-1])
    elif s == "G":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1] + 1)
        sumB.append(sumB[-1])
    elif s == "B":
        sumR.append(sumR[-1])
        sumG.append(sumG[-1])
        sumB.append(sumB[-1] + 1)


for i, s in enumerate(S):
    not_cnt = 0
    for k in range(1, min(i + 1, N - i)):
        L, R = S[i - k], S[i + k]
        if s != L and s != R and L != R:
            not_cnt += 1

    cnt = 0
    if s == "R":
        cnt += sumG[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumG[-1] - sumG[i + 1])
    elif s == "G":
        cnt += sumR[i] * (sumB[-1] - sumB[i + 1])
        cnt += sumB[i] * (sumR[-1] - sumR[i + 1])
    elif s == "B":
        cnt += sumG[i] * (sumR[-1] - sumR[i + 1])
        cnt += sumR[i] * (sumG[-1] - sumG[i + 1])

    cnt -= not_cnt
    ans += cnt


print(ans)