Buggy python submission (verdict: Runtime Error):
import collections

N = int(input())
l = list(map(int, input().split()))

a = []
b = []
a_f = 0
b_f = 0
a_s = 0
b_s = 0
for i in range(N):
    if i%2 == 0:
        a.append(l[i])
    else:
        b.append(l[i])
        
c_a = collections.Counter(a)
c_b = collections.Counter(b)

a_f = c_a.most_common()[0]
b_f = c_b.most_common()[0]

if a_f[0] != b_f[0]:
    print(N - a_f[1] - b_f[1])

elif len(set(a)) == 1 and len(set(b)) == 1:
    print(int(N/2))
elif len(set(a)) == 1:
    print(int(N/2 - c_b.most_common()[1][1]))
elif len(set(b)) == 1:
    print(int(N/2 - c_a.most_common()[1][1]))
elif a_f[1] == b_f[1]:
    second_a = c_a.most_common()[1][1]
    second_b = c_b.most_common()[1][1]
    if second_a >= second_b:
        print(int(N - b_f[1] - second_a)
    else:
        print(int(N - a_f[1] - second_b)
elif a_f[1] > b_f[1]:
    print(int(N - a_f[1] - c_b.most_common()[1][1]))
else:
    print(int(N - b_f[1] - c_a.most_common()[1][1]))

Fixed submission:
import collections

N = int(input())
l = list(map(int, input().split()))

a = []
b = []
a_f = 0
b_f = 0
a_s = 0
b_s = 0
for i in range(N):
    if i%2 == 0:
        a.append(l[i])
    else:
        b.append(l[i])
        
c_a = collections.Counter(a)
c_b = collections.Counter(b)

a_f = c_a.most_common()[0]
b_f = c_b.most_common()[0]

if a_f[0] != b_f[0]:
    print(N - a_f[1] - b_f[1])

elif len(set(a)) == 1 and len(set(b)) == 1:
    print(int(N/2))
elif len(set(a)) == 1:
    print(int(N/2 - c_b.most_common()[1][1]))
elif len(set(b)) == 1:
    print(int(N/2 - c_a.most_common()[1][1]))
elif a_f[1] == b_f[1]:
    second_a = c_a.most_common()[1][1]
    second_b = c_b.most_common()[1][1]
    if second_a >= second_b:
        print(int(N - b_f[1] - second_a))
    else:
        print(int(N - a_f[1] - second_b))
elif a_f[1] > b_f[1]:
    print(int(N - a_f[1] - c_b.most_common()[1][1]))
else:
    print(int(N - b_f[1] - c_a.most_common()[1][1]))

Buggy python submission (verdict: Runtime Error):
import collections

N = int(input())
l = list(map(int, input().split()))

a = []
b = []
a_f = 0
b_f = 0
a_s = 0
b_s = 0
for i in range(N):
    if i%2 == 0:
        a.append(l[i])
    else:
        b.append(l[i])
        
c_a = collections.Counter(a)
c_b = collections.Counter(b)

a_f = c_a.most_common()[0]
b_f = c_b.most_common()[0]

if a_f[0] != b_f[0]:
    print(N - a_f[1] - b_f[1])

elif len(set(a)) == 1 and len(set(b)) == 1:
    print(int(N/2))
elif len(set(a)) == 1:
    print(int(N/2 - c_b.most_common()[1][1]))
elif len(set(b)) == 1:
    print(int(N/2 - c_a.most_common()[1][1]))
elif a_f[1] == b_f[1]:
    if c_a.most_common()[1][1] >= c_b.most_common()[1][1]:
        print(int(N - b_f[1] - c_a.most_common()[1][1]))
    else:
        print(int(N - a_f[1] - b_a.most_common()[1][1]))
elif a_f[1] > b_f[1]:
    print(int(N - a_f[1] - c_b.most_common()[1][1]))
else:
    print(int(N - b_f[1] - c_a.most_common()[1][1]))

Fixed submission:
import collections

N = int(input())
l = list(map(int, input().split()))

a = []
b = []
a_f = 0
b_f = 0
a_s = 0
b_s = 0
for i in range(N):
    if i%2 == 0:
        a.append(l[i])
    else:
        b.append(l[i])
        
c_a = collections.Counter(a)
c_b = collections.Counter(b)

a_f = c_a.most_common()[0]
b_f = c_b.most_common()[0]

if a_f[0] != b_f[0]:
    print(N - a_f[1] - b_f[1])

elif len(set(a)) == 1 and len(set(b)) == 1:
    print(int(N/2))
elif len(set(a)) == 1:
    print(int(N/2 - c_b.most_common()[1][1]))
elif len(set(b)) == 1:
    print(int(N/2 - c_a.most_common()[1][1]))
elif a_f[1] == b_f[1]:
    second_a = c_a.most_common()[1][1]
    second_b = c_b.most_common()[1][1]
    if second_a >= second_b:
        print(int(N - b_f[1] - second_a))
    else:
        print(int(N - a_f[1] - second_b))
elif a_f[1] > b_f[1]:
    print(int(N - a_f[1] - c_b.most_common()[1][1]))
else:
    print(int(N - b_f[1] - c_a.most_common()[1][1]))