Buggy python submission (verdict: Time Limit Exceeded):
n=int(input())
s=input()

#logging.debug("デバッグスタート") #
ans = 0
for i in range(n):
    for j in range(i + 1, n):
        if s[i] != s[j]:
            if (s[i] == "R" and s[j]=="G") or (s[i] == "G" and s[j]=="R"):
                ans += s[j + 1 :].count("B")
                if (j - i + j) < n:
                    if s[j - i + j] == "B":
                        ans -= 1
                    continue
            if (s[i] == "R" and s[j]=="B") or (s[i] == "B" and s[j]=="R"):
                ans += s[j + 1 :].count("G")
                if (j - i + j) < n:
                    if s[j - i + j] == "G":
                        ans -= 1
                    continue
            if (s[i] == "B" and s[j]=="G") or (s[i] == "G" and s[j]=="B"):
                ans += s[j + 1 :].count("R")
                if (j - i + j) < n:
                    if s[j - i + j] == "R":
                        ans -= 1
                    continue

print(ans)

Fixed submission:
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0

for i in range(0,N):
    j = 1
    while i + (2 * j) <= N-1:
        if S[i] != S[i + j] and S[i + j] != S[i + (2*j)] and S[i] != S[i + (2*j)]:
            cou += 1
        j += 1

print(S.count("R")*S.count("G")*S.count("B")-cou)

Buggy python submission (verdict: Time Limit Exceeded):
n=int(input())
s=input()

#logging.debug("デバッグスタート") #
ans = 0
for i in range(n):
    for j in range(i + 1, n):
        if s[i] != s[j]:
            if (s[i] == "R" and s[j]=="G") or (s[i] == "G" and s[j]=="R"):
                ans += s[j + 1 :].count("B")
                if (j - i + j) < n:
                    if s[j - i + j] == "B":
                        ans -= 1
                    continue
            if (s[i] == "R" and s[j]=="B") or (s[i] == "B" and s[j]=="R"):
                ans += s[j + 1 :].count("G")
                if (j - i + j) < n:
                    if s[j - i + j] == "G":
                        ans -= 1
                    continue
            if (s[i] == "B" and s[j]=="G") or (s[i] == "G" and s[j]=="B"):
                ans += s[j + 1 :].count("R")
                if (j - i + j) < n:
                    if s[j - i + j] == "R":
                        ans -= 1
                    continue

print(ans)

Fixed submission:
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0

for i in range(0,N):
    j = 1
    while i + (2 * j) <= N-1:
        if S[i] != S[i + j] and S[i + j] != S[i + (2*j)] and S[i] != S[i + (2*j)]:
            cou += 1
        j += 1

print(S.count("R")*S.count("G")*S.count("B")-cou)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = list(input())

sum = 0
for i in range(N-2):
    for j in range(i+1,N):
        for k in range(j+1, N):
#            print(i, j, k)
            if S[i] == S[j] or S[j] == S[k] or S[i] == S[k]:
                continue
            elif j - i == k - j:
                continue
            else:
                sum += 1

print(sum)

Fixed submission:
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0

for i in range(0,N):
    j = 1
    while i + (2 * j) <= N-1:
        if S[i] != S[i + j] and S[i + j] != S[i + (2*j)] and S[i] != S[i + (2*j)]:
            cou += 1
        j += 1

print(S.count("R")*S.count("G")*S.count("B")-cou)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = list(input())

from math import gcd
sum = 0
for i in range(N-2):
    for j in range(i+1,N):
        for k in range(j+1, N):
#            print(i, j, k)
            if S[i] == S[j] or S[j] == S[k] or S[i] == S[k]:
                continue
            elif j - i == k - j:
                continue
            else:
                sum += 1

print(sum)

Fixed submission:
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0

for i in range(0,N):
    j = 1
    while i + (2 * j) <= N-1:
        if S[i] != S[i + j] and S[i + j] != S[i + (2*j)] and S[i] != S[i + (2*j)]:
            cou += 1
        j += 1

print(S.count("R")*S.count("G")*S.count("B")-cou)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0
for i in range(N):
    for j in range(i, N):
        if S[i] != S[j]:
            for k in range(j, N):
                if S[i] != S[k] and S[j] != S[k]:
                    if j - i != k - j:
                        cou +=1
print(cou)

Fixed submission:
N = int(input())  #数字
S = list(input()) #スペース抜きの複数行,１文字ずつ

cou = 0

for i in range(0,N):
    j = 1
    while i + (2 * j) <= N-1:
        if S[i] != S[i + j] and S[i + j] != S[i + (2*j)] and S[i] != S[i + (2*j)]:
            cou += 1
        j += 1

print(S.count("R")*S.count("G")*S.count("B")-cou)