Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
"""
Created on Sun Mar 22 13:54:24 2020

@author: naoki
"""
import sys
f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(f.readline())
a = list(map(lambda x:int(x)-1,list(f.readline())))
   
all_odd = 0
kai = [0] * N

if (0 not in a) and (1 not in a):
    print(0)
    sys.exit()
if (1 not in a) and (2 not in a):
    print(0)
    sys.exit()
if (0 not in a) and (2 not in a):
    print(0)
    sys.exit()
    
for k in range(1,N):
    count = 0
    p = k
    for _ in range(N):
        if p % 2 == 1:
            kai[k] = kai[k-1] + count
            break
        p = p/2
        count += 1

all_num = 0
for k in range(N):
    if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
        all_num += 1

if all_num % 2 == 1:
    print(1)
elif 1 in a:
    print(0)
else:
    for i in range(N):
        a[i] = a[i]/2
    for k in range(N):
        if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
            all_num += 1
    if all_num % 2 == 1:
        print(2)
    else:
        print(0)

Fixed submission:
# -*- coding: utf-8 -*-
"""
Created on Sun Mar 22 13:54:24 2020

@author: naoki
"""
import sys
#f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(input())
a = list(map(lambda x:int(x)-1,list(input())))
   
all_odd = 0
kai = [0] * N

if (0 not in a) and (1 not in a):
    print(0)
    sys.exit()
if (1 not in a) and (2 not in a):
    print(0)
    sys.exit()
if (0 not in a) and (2 not in a):
    print(0)
    sys.exit()
    
for k in range(1,N):
    count = 0
    p = k
    for _ in range(N):
        if p % 2 == 1:
            kai[k] = kai[k-1] + count
            break
        p = p/2
        count += 1

all_num = 0
for k in range(N):
    if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
        all_num += 1

if all_num % 2 == 1:
    print(1)
elif 1 in a:
    print(0)
else:
    for i in range(N):
        a[i] = a[i]/2
    for k in range(N):
        if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
            all_num += 1
    if all_num % 2 == 1:
        print(2)
    else:
        print(0)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-
"""
Created on Sun Mar 22 13:54:24 2020

@author: naoki
"""
import sys
#f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(input())
a = list(map(lambda x:int(x)-1,list(input())))
   
all_odd = 0
kai = [0] * N

if (0 not in a) and (1 not in a):
    print(0)
    sys.exit()
if (1 not in a) and (2 not in a):
    print(0)
    sys.exit()
if (0 not in a) and (2 not in a):
    print(0)
    sys.exit()
    
for k in range(1,N):
    count = 0
    p = k
    for _ in range(N):
        if p % 2 == 1:
            kai[k] = kai[k-1] + count
            break
        p = p/2
        count += 1

all_num = 0
for k in range(N):
    if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
        all_num += 1

if all_num % 2 == 1:
    print(1)
elif 1 in a:
    print(0)
else:
    for i in range(N):
        a[i] = a[i]/2
    for k in range(N):
        if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
            all_num += 1
    if all_num % 2 == 1:
        print(2)
    else:
        print(0)

Fixed submission:
# -*- coding: utf-8 -*-
"""
Created on Sun Mar 22 13:54:24 2020

@author: naoki
"""
import sys
#f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(input())
a = list(map(lambda x:int(x)-1,list(input())))
   
all_odd = 0
kai = [0] * N

if (0 not in a) and (1 not in a):
    print(0)
    sys.exit()
if (1 not in a) and (2 not in a):
    print(0)
    sys.exit()
if (0 not in a) and (2 not in a):
    print(0)
    sys.exit()
    
for k in range(1,N):
    count = 0
    p = k
    for _ in range(N):
        if p % 2 == 1:
            kai[k] = kai[k-1] + count
            break
        p = p/2
        count += 1

all_num = 0
for k in range(N):
    if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
        all_num += 1

if all_num % 2 == 1:
    print(1)
elif 1 in a:
    print(0)
else:
    for i in range(N):
        a[i] = a[i]/2
    for k in range(N):
        if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
            all_num += 1
    if all_num % 2 == 1:
        print(2)
    else:
        print(0)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
"""
Created on Sat Mar 21 20:58:03 2020

@author: naoki
"""

from collections import deque
f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(input())
a = list(map(int, list(input())))

flag1 = [-100, -100]
flag2 = [-100, -100]
flag3 = [-100, -100]

for i in range(N//2):
    if a[i] == 2:
        flag1[0] = i
    if a[N-i-1] ==2 :
        flag1[1] = N-i-1
    if (a[i] == 1 and a[i+1] == 3) or (a[i] == 3 and a[i+1] == 1):
        flag2[0] = i
    if (a[N-i-1] == 1 and a[N-i-2] == 3) or (a[N-i-1] == 3 and a[N-i-2] == 1):
        flag2[1] = N-i-1
    
    if flag1[0] > 0 and flag1[1] > 0:
        b = a[0:flag1[0]].extend(a[flag1[1]:])
        break
    if flag2[0] > 0 and flag2[1] > 0:
        b = a[0:flag2[0]].extend(a[flag2[1]:])
        break
else:
    b = a
last = []
for i in range(len(b)-1):
    if b[i] != b[i+1]:
        last.append(b[i],b[i+1])

for i in range(len(last)-1):
    last = []
    for p in range(len(last) - i):
        last[p] = abs(last[p+1] - last[p])
print(last[0])
        

Fixed submission:
# -*- coding: utf-8 -*-
"""
Created on Sun Mar 22 13:54:24 2020

@author: naoki
"""
import sys
#f = open("C:/Users/naoki/Desktop/Atcoder/input.txt")
N = int(input())
a = list(map(lambda x:int(x)-1,list(input())))
   
all_odd = 0
kai = [0] * N

if (0 not in a) and (1 not in a):
    print(0)
    sys.exit()
if (1 not in a) and (2 not in a):
    print(0)
    sys.exit()
if (0 not in a) and (2 not in a):
    print(0)
    sys.exit()
    
for k in range(1,N):
    count = 0
    p = k
    for _ in range(N):
        if p % 2 == 1:
            kai[k] = kai[k-1] + count
            break
        p = p/2
        count += 1

all_num = 0
for k in range(N):
    if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
        all_num += 1

if all_num % 2 == 1:
    print(1)
elif 1 in a:
    print(0)
else:
    for i in range(N):
        a[i] = a[i]/2
    for k in range(N):
        if kai[-1] <= kai[k] + kai[N-1-k] and a[k] == 1:
            all_num += 1
    if all_num % 2 == 1:
        print(2)
    else:
        print(0)