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

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    for k in range(j,n):
      if j-i==k-j:
        if s[j]!=s[k] and s[k]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    for k in range(j,n):
      if j-i==k-j:
        if s[j]!=s[k] and s[k]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    for k in range(j,n):
#      print(i,j,k)
      if j-i==k-j:
        if s[i]!=s[j] and s[j]!=s[k] and s[k]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    for k in range(j,n):
#      print(i,j,k)
      if j-i==k-j:
        if s[i]!=s[j] and s[j]!=s[k] and s[k]!=s[i]:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)

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

r=s.count('R')
g=s.count('G')
b=s.count('B')

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    for k in range(j,n):
#      print(i,j,k)
      if s[i]!=s[j] and s[j]!=s[k] and s[k]!=s[i]:
        if j-i==k-j:
          ng+=1
print(all-ng)

Fixed submission:
n=int(input())
s=input()

#r=s.count('R')
#g=s.count('G')
#b=s.count('B')

r,g,b=0,0,0

for i in range(0,n):
  if s[i]=='R':
    r+=1
  elif s[i]=='G':
    g+=1
  else:
    b+=1

ng=0

all=r*g*b

#NGパターン数の洗い出し
for i in range(0,n-2):
  for j in range(i,n-1):
    if s[i]==s[j]:
      continue
    else:
      if j*2-i<=n-1:
#        print(i,j,j*2-i)
        if s[j]!=s[j*2-i] and s[j*2-i]!=s[i]:
          ng+=1
print(all-ng)