Lucky numbers

def diff (s, t):
    x = 0
    for i in range(0, len(s)):
        if s[i] != t[i]:
            x += 1
    return x

def a (s, t):
    j = 0
    for x in s:
        if x == t:
            j += 1
    return j

s = raw_input();
n = len(s)
ans = n - a(s, "7") - a(s, "0")
if s[0] == "0":
    ans += 1

if n % 3 == 0:
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '4':
                x += 1
        else:
            if s[i] != '3':
                x += 1
    ans = min(ans, x)
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '3':
                x += 1
        else:
            if s[i] != '4':
                x += 1
    ans = min(ans, x)
if n % 3 == 0:
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '6':
                x += 1
        else:
            if s[i] != '8' and s[i] != '1':
                x += 1
    ans = min(ans, x)
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '8' and s[i] != '1':
                x += 1
        else:
            if s[i] != '6':
                x += 1
    ans = min(ans, x)
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '5':
                x += 1
        else:
            if s[i] != '9' and s[i] != '2':
                x += 1
    ans = min(ans, x)
    x = 0
    for i in range(0, n):
        if i % 2 == 0:
            if s[i] != '9' and s[i] != '2':
                x += 1
        else:
            if s[i] != '5':
                x += 1
    ans = min(ans, x)

print(ans)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED