Buggy python submission (verdict: Time Limit Exceeded):
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(n-2):
        for j in range(i+1,n-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                else:
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()

Fixed submission:
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(n-2):
        for j in range(i+1,n-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                else:
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(n-2):
        for j in range(i+1,n-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    elif s[j] == 'B':
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    elif s[j] == 'B':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                elif s[i] == 'B':
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    elif s[j] == 'R':
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()

Fixed submission:
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(n-2):
        for j in range(i+1,n-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                else:
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(len(s)-2):
        for j in range(i+1,len(s)-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    elif s[j] == 'B':
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    elif s[j] == 'B':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                elif s[i] == 'B':
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    elif s[j] == 'R':
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()

Fixed submission:
def solve(n, s):
    rlist, glist, blist = [0 for _ in range(n)], [0 for _ in range(n)], [0 for _ in range(n)]
    rcount, gcount, bcount = 0, 0, 0
    for i in range(n-1):
        if s[n-1-i] == 'R':
            rcount += 1
        if s[n-1-i] == 'G':
            gcount += 1
        if s[n-1-i] == 'B':
            bcount += 1
        rlist[n-2-i], glist[n-2-i], blist[n-2-i] = rcount, gcount, bcount
        
    ans = 0

    for i in range(n-2):
        for j in range(i+1,n-1):
            if s[i] != s[j]:
                if s[i] == 'R':
                    if s[j] == 'G':
                        ans += blist[j] - ( 1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
                elif s[i] == 'G':
                    if s[j] == 'R':
                        ans += blist[j] - (1 if 2*j-i < n and s[2*j-i] == 'B' else 0)
                    else:
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                else:
                    if s[j] == 'G':
                        ans += rlist[j] - (1 if 2*j-i < n and s[2*j-i] == 'R' else 0)
                    else:
                        ans += glist[j] - (1 if 2*j-i < n and s[2*j-i] == 'G' else 0)
    
    return ans

def main():
    n = int(input())
    s = input()
    print(solve(n, s))

if __name__ == '__main__':
    main()