Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

#ans = []
#temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    #global ans
    #global temp_array
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #if i == N_l-1:
        #    temp_ans = ans
        #else:
        for s in temp_ans:
            if s[0] != N[i] and N[i] not in s:
                temp_ans.append(N[i]+s)
                    #print(N[i]+s)
        #print(temp_ans)
        #ans += temp_array
        #temp_ans = ans
        #temp_array = []
    return len(temp_ans) % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

ans = []
temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    global ans
    global temp_array
    for i in range(N_l)[::-1]:
        ans += N[i]
        if i == N_l-1:
            temp_ans = ans
        else:
            for s in temp_ans:
                if s[0] != N[i] and N[i] not in s:
                    temp_ans.append(N[i]+s)
                    #print(N[i]+s)
        #print(temp_ans)
        ans += temp_array
        temp_ans = ans
        temp_array = []
    return len(ans) % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin

ans = []
temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    global ans
    global temp_array
    for i in range(N_l)[::-1]:
        ans += N[i]
        if i == -N_l+1:
            temp_ans = ans
        if len(temp_ans) != 0:
            temp_ans += [N[i]+s for s in temp_ans if s[0] != N[i] and N[i] not in s]
        ans += temp_array
        temp_ans = ans
        temp_array = []
    return len(ans) % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
#import sys
#sys.setrecursionlimit(10**7)

ans = []
temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    #print(range(N_l)[::-1])
    #print(range(N_l))
    #global ans 
    #ans.append(N[-1])
    global temp_ans
    global ans
    for i in range(N_l)[::-1]:
    #for i in range(N_l):
        ans += N[i]
        if i == -N_l+1:
            temp_ans = ans
        b(N, N[i], i)
        #global temp_ans
        global temp_array
        ans += temp_array
        temp_ans = ans
        #print(temp_ans)
        #print(temp_array)
        temp_array = []
        #print(ans)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    global temp_array
    global temp_ans
    """
    if len(org_array) == 0:
        #global temp_array
        #global ans
        #ans += temp_array
        #print(temp_array)
        #temp_array = []
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        #print(temp_array)
    """
    if len(temp_ans) != 0:
        temp_ans += [temp+s for s in temp_ans if s[0] != temp and temp not in s]

        #for tmp in temp_array:
        #    b(org_array, tmp, i+1)
        """
        if temp not in temp_array:
            temp_array.append(temp)
        new_temp = temp
        b(org_array, new_temp, i+1)
        if org_array[i+1] not in temp:
            temp += org_array[i+1]
            if temp not in temp_array:
                temp_array.append(temp)
            b(org_array, temp, i+1)
        #print("org: "+org_array[i+1])
        #print(temp)
        #b(org_array, temp, i+1)
        """


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
#import sys
#sys.setrecursionlimit(10**7)

ans = []
temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    #print(range(N_l)[::-1])
    #print(range(N_l))
    #global ans 
    #ans.append(N[-1])
    global temp_ans
    global ans
    for i in range(N_l)[::-1]:
    #for i in range(N_l):
        ans += N[i]
        if i == -N_l+1:
            temp_ans = ans
        b(N, N[i], i)
        #global temp_ans
        global temp_array
        ans += temp_array
        temp_ans = ans
        #print(temp_ans)
        #print(temp_array)
        temp_array = []
        #print(ans)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    global temp_array
    global temp_ans
    """
    if len(org_array) == 0:
        #global temp_array
        #global ans
        #ans += temp_array
        #print(temp_array)
        #temp_array = []
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        #print(temp_array)
    """
    if len(temp_ans) != 0:
        temp_array += [temp+s for s in temp_ans if s[0] != temp and temp not in s]

        #for tmp in temp_array:
        #    b(org_array, tmp, i+1)
        """
        if temp not in temp_array:
            temp_array.append(temp)
        new_temp = temp
        b(org_array, new_temp, i+1)
        if org_array[i+1] not in temp:
            temp += org_array[i+1]
            if temp not in temp_array:
                temp_array.append(temp)
            b(org_array, temp, i+1)
        #print("org: "+org_array[i+1])
        #print(temp)
        #b(org_array, temp, i+1)
        """


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**7)

ans = []
temp_array = []
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    #print(range(N_l)[::-1])
    #print(range(N_l))
    #global ans 
    #ans.append(N[-1])
    global temp_ans
    global ans
    for i in range(N_l)[::-1]:
    #for i in range(N_l):
        ans += N[i]
        if i == -N_l+1:
            temp_ans = ans
        b(N, N[i], i)
        #global temp_ans
        global temp_array
        ans += temp_array
        temp_ans = ans
        #print(temp_ans)
        #print(temp_array)
        temp_array = []
        #print(ans)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    global temp_array
    global temp_ans
    """
    if len(org_array) == 0:
        #global temp_array
        #global ans
        #ans += temp_array
        #print(temp_array)
        #temp_array = []
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        #print(temp_array)
    """
    if len(temp_ans) != 0:
        temp_array += [temp+s for s in temp_ans if s[0] != temp and temp not in s]

        #for tmp in temp_array:
        #    b(org_array, tmp, i+1)
        """
        if temp not in temp_array:
            temp_array.append(temp)
        new_temp = temp
        b(org_array, new_temp, i+1)
        if org_array[i+1] not in temp:
            temp += org_array[i+1]
            if temp not in temp_array:
                temp_array.append(temp)
            b(org_array, temp, i+1)
        #print("org: "+org_array[i+1])
        #print(temp)
        #b(org_array, temp, i+1)
        """


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**7)

ans = []
temp_array = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    #print(range(N_l)[::-1])
    #print(range(N_l))
    #for i in range(N_l)[::-1]:
    for i in range(N_l):
        global temp_array
        temp_array = []
        b(N, N[i], i)
        #print(ans)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    ans.append(N[-1])
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    global temp_array
    if len(org_array)-1 == i:
        global ans
        ans += temp_array
        temp_array = []
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        #print(temp_array)
        if temp not in temp_array:
            temp_array.append(temp)
        b(org_array, temp, i+1)
        if org_array[i+1] not in temp:
            temp += org_array[i+1]
            if temp not in temp_array:
                temp_array.append(temp)
            b(org_array, temp, i+1)
        #print("org: "+org_array[i+1])
        #print(temp)
        #b(org_array, temp, i+1)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
import sys
sys.setrecursionlimit(10**7)

ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    for i in range(N_l):
        b(N, N[i], i)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    for i in range(N_l):
        ans.append(N[i])
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    if len(org_array)-1 == i:
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        if org_array[i+1] not in temp:
            b(org_array, temp, i+1)
            temp += org_array[i+1]
            ans.append(temp)
        #print("org: "+org_array[i+1])
        #print(temp)
        b(org_array, temp, i+1)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
from sys import stdin
import sys
sys.setrecursionlimit(10**10)

ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    for i in range(N_l):
        b(N, N[i], i)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    for i in range(N_l):
        ans.append(N[i])
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    if len(org_array)-1 == i:
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        if org_array[i+1] not in temp:
            b(org_array, temp, i+1)
            temp += org_array[i+1]
            ans.append(temp)
        #print("org: "+org_array[i+1])
        #print(temp)
        b(org_array, temp, i+1)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
from sys import stdin
import sys
sys.setrecursionlimit(10*10)

ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    for i in range(N_l):
        b(N, N[i], i)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    for i in range(N_l):
        ans.append(N[i])
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    if len(org_array)-1 == i:
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        if org_array[i+1] not in temp:
            b(org_array, temp, i+1)
            temp += org_array[i+1]
            ans.append(temp)
        #print("org: "+org_array[i+1])
        #print(temp)
        b(org_array, temp, i+1)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
from sys import stdin

ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S, N)

    #% (10^9 + 7)
    #return count_0
    N_l = len(N)
    for i in range(N_l):
        b(N, N[i], i)
    #print(list(set(ans)))
    #print(10**9 + 7)

    # 2
    #return len(list(set(ans))) % (10**9 + 7)
    for i in range(N_l):
        ans.append(N[i])
    #print(ans)
    return len(ans) % (10**9 + 7)


def b(org_array, temp, i):
    if len(org_array)-1 == i:
        return
    else:
        #print("org array:"+org_array)
        #ans.append(temp)
        #print(temp)
        if org_array[i+1] not in temp:
            b(org_array, temp, i+1)
            temp += org_array[i+1]
            ans.append(temp)
        #print("org: "+org_array[i+1])
        #print(temp)
        b(org_array, temp, i+1)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()


Fixed submission:
from sys import stdin
import math
import itertools


def combinations_count(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))

# これだと、O(n*n)
"""
temp_ans = []


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    N_l = len(N)
    global temp_ans
    for i in range(N_l)[::-1]:
        temp_ans += N[i]
        #print(temp_ans)
        for s in temp_ans:
            #print(s)
            if N[i] not in s:
                temp_ans.append(N[i]+s)
    #print(temp_ans)
    return len(temp_ans) % (10**9 + 7)
"""


def problem_a(input_string):
    S = int(input_string[0].rstrip())
    N = input_string[1].rstrip()
    #print(S)
    dic = {}
    c = 0
    for i in range(S)[::-1]:
        if N[i] not in dic:
            dic[N[i]] = 1
            #c += i+1
        else:
            dic[N[i]] += 1

    c = 1
    for key, value in dic.items():
        c *= (value+1)
    c -= 1
    """
    c += 2**len(dic.keys())-1
    #print(c)
    #c += S
    for key, value in dic.items():
        if value > 1:
            #c -= (value-1)
            c += 2**(len(dic.keys()))-1
            #print(c)
    #for key, value in dic.items():
    for key, value in dic.items():
        if value > 1:
            if len(dic.keys()) != S:
                c -= 2**(S-len(dic.keys())-1)
    """
            #print(c)
        #else:
    #c += (S-len(dic.keys()))
    """
    s_N = sorted(N)
    for i in range(S-1):
        if s_N[i] != s_N[i+1]:
            c += 2**(i+2)
    """
    """
    for key, value in dic.items():
        if value > 1:
            c += 2**(len(dic.items())-value)
        else:
            c += 2**(len(dic.items())-value)
    """
    #combinations_count(len(, r)

    return c % (10**9 + 7)


def main():
    input_line = stdin.readlines()
    answer = problem_a(input_line)
    print(answer)


if __name__ == '__main__':
    main()