Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
ans = 0
for X in range(1,2**len(D)):
  k = format(X,'b').zfill(len(D))
  cur = 1
  for i in range(len(k)):
    if k[i] == '1':
      cur *= (D[i]%(10**9+7))
  ans += (cur%(10**9+7))
print(ans%(10**9+7))

Fixed submission:
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
ans = 1
for i in range(len(D)):
  ans *= (D[i]+1)
  ans = ans%(10**9+7)
print((ans-1)%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
def Base_10_to_n(X, n):
    if (int(X/n)):
        return Base_10_to_n(int(X/n), n)+str(X%n)
    return str(X%n)
ans = 0
n = 2
for X in range(1,2**len(D)):
  k = Base_10_to_n(X, n).zfill(len(D))
  cur = 1
  for i in range(len(k)):
    if k[i] == '1':
      cur *= (D[i]%(10**9+7))
  ans += (cur%(10**9+7))
print(ans%(10**9+7))

Fixed submission:
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
ans = 1
for i in range(len(D)):
  ans *= (D[i]+1)
  ans = ans%(10**9+7)
print((ans-1)%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
def Base_10_to_n(X, n):
    if (int(X/n)):
        return Base_10_to_n(int(X/n), n)+str(X%n)
    return str(X%n)
ans = 0
n = 2
for X in range(1,2**len(D)):
  k = Base_10_to_n(X, n).zfill(len(D))
  cur = 1
  for i in range(len(k)):
    if k[i] == '1':
      cur *= D[i]
  ans += cur
print(ans%(10**9+7))

Fixed submission:
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
ans = 1
for i in range(len(D)):
  ans *= (D[i]+1)
  ans = ans%(10**9+7)
print((ans-1)%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
def Base_10_to_n(X, n):
    if (int(X/n)):
        return Base_10_to_n(int(X/n), n)+str(X%n)
    return str(X%n)
ans = 0
n = 2
for X in range(1,2**len(D)):
  k = Base_10_to_n(X, n).zfill(len(D))
  cur = 1
  for i in range(len(k)):
    if k[i] == '1':
      cur *= D[i]
  ans = (ans+cur)%(10**9+7)
print(ans)

Fixed submission:
N = int(input())
S = input()
L = [chr(ord('a') + i) for i in range(26)]
cnt = [0]*26
for i in range(len(S)):
  cnt[ord(S[i])-97] += 1
D = []
for i in range(26):
  if cnt[i] != 0:
    D.append(cnt[i])
ans = 1
for i in range(len(D)):
  ans *= (D[i]+1)
  ans = ans%(10**9+7)
print((ans-1)%(10**9+7))