Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    RGB = []
    for i in range(N):
        RGB.append(Counter(S[:i+1]))
        
    for i in range(N-1):
        for j in range(i+1, N):
            if S[i] == S[j]:
                continue
            c = 'RGB'.replace(S[i], '')
            c = c.replace(S[j], '')
            ans += RGB[-1][c] - RGB[j][c]
            if 2*j - i < N and S[2*j-i] == c:
                ans -= 1
    print(ans)

main()

Fixed submission:
from collections import Counter
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    r, g, b = [0 for _ in range(N+1)], [0 for _ in range(N+1)], [0 for _ in range(N+1)]
    for i in range(N):
        r[i+1], g[i+1], b[i+1] = r[i], g[i], b[i]
        if S[i] == "R":
            r[i+1] += 1
        elif S[i] == "G":
            g[i+1] += 1
        else:
            b[i+1] += 1
    
    for i in range(1, N-1):
        if S[i] == "R":
            ans += g[i] * (b[N] - b[i+1]) + b[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "B"}:
                    ans -= 1
        
        elif S[i] == "G":
            ans += r[i] * (b[N] - b[i+1]) + b[i] * (r[N] - r[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"R", "B"}:
                    ans -= 1
        elif S[i] == "B":
            ans += g[i] * (r[N] - r[i+1]) + r[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "R"}:
                    ans -= 1
    print(ans)

main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    for i in range(N-1):
        for j in range(i+1, N):
            if S[i] == S[j]:
                continue
            c = 'RGB'.replace(S[i], '')
            c = c.replace(S[j], '')
            ans += S[j+1:].count(c)
            if 2*j - i < N and S[2*j-i] == c:
                ans -= 1
    print(ans)

main()

Fixed submission:
from collections import Counter
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    r, g, b = [0 for _ in range(N+1)], [0 for _ in range(N+1)], [0 for _ in range(N+1)]
    for i in range(N):
        r[i+1], g[i+1], b[i+1] = r[i], g[i], b[i]
        if S[i] == "R":
            r[i+1] += 1
        elif S[i] == "G":
            g[i+1] += 1
        else:
            b[i+1] += 1
    
    for i in range(1, N-1):
        if S[i] == "R":
            ans += g[i] * (b[N] - b[i+1]) + b[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "B"}:
                    ans -= 1
        
        elif S[i] == "G":
            ans += r[i] * (b[N] - b[i+1]) + b[i] * (r[N] - r[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"R", "B"}:
                    ans -= 1
        elif S[i] == "B":
            ans += g[i] * (r[N] - r[i+1]) + r[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "R"}:
                    ans -= 1
    print(ans)

main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    for i in range(N-1):
        for j in range(i, N):
            if S[i] == S[j]:
                continue
            c = 'RGB'.replace(S[i], '')
            c = c.replace(S[j], '')
            ans += S[j+1:].count(c)
            if 2*j - i < N and S[2*j-i] == c:
                ans -= 1
    print(ans)

main()

Fixed submission:
from collections import Counter
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    r, g, b = [0 for _ in range(N+1)], [0 for _ in range(N+1)], [0 for _ in range(N+1)]
    for i in range(N):
        r[i+1], g[i+1], b[i+1] = r[i], g[i], b[i]
        if S[i] == "R":
            r[i+1] += 1
        elif S[i] == "G":
            g[i+1] += 1
        else:
            b[i+1] += 1
    
    for i in range(1, N-1):
        if S[i] == "R":
            ans += g[i] * (b[N] - b[i+1]) + b[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "B"}:
                    ans -= 1
        
        elif S[i] == "G":
            ans += r[i] * (b[N] - b[i+1]) + b[i] * (r[N] - r[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"R", "B"}:
                    ans -= 1
        elif S[i] == "B":
            ans += g[i] * (r[N] - r[i+1]) + r[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "R"}:
                    ans -= 1
    print(ans)

main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    for i in range(N-1):
        for j in range(i, N):
            for k in range(j, N):
                if (S[i] != S[j] and S[j] != S[k] and S[i] != S[k]) and (j - i != k - j):
                    ans += 1
    print(ans)

main()

Fixed submission:
from collections import Counter
import sys
input = sys.stdin.readline

def main():
    N = int(input())
    S = input()
    ans = 0
    r, g, b = [0 for _ in range(N+1)], [0 for _ in range(N+1)], [0 for _ in range(N+1)]
    for i in range(N):
        r[i+1], g[i+1], b[i+1] = r[i], g[i], b[i]
        if S[i] == "R":
            r[i+1] += 1
        elif S[i] == "G":
            g[i+1] += 1
        else:
            b[i+1] += 1
    
    for i in range(1, N-1):
        if S[i] == "R":
            ans += g[i] * (b[N] - b[i+1]) + b[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "B"}:
                    ans -= 1
        
        elif S[i] == "G":
            ans += r[i] * (b[N] - b[i+1]) + b[i] * (r[N] - r[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"R", "B"}:
                    ans -= 1
        elif S[i] == "B":
            ans += g[i] * (r[N] - r[i+1]) + r[i] * (g[N] - g[i+1])
            for j in range(1, min(i, N-i-1)+1):
                if {S[i-j], S[i+j]} == {"G", "R"}:
                    ans -= 1
    print(ans)

main()