def add(arr1, arr2):
l = max(len(arr1), len(arr2))
result = [0 for j in range(l)]
c = 0
i = len(arr1) - 1
j = len(arr2) - 1
r = 0
l -= 1
while i >= 0 and j >= 0:
r = arr1[i] + arr2[j] + c
i -= 1
j -= 1
c = r // 10
result[l] = r % 10
l -= 1
while i >= 0:
r = arr1[i] + c
i -= 1
c = r // 10
result[l] = r % 10
l -= 1
while j >= 0:
r = arr1[j] + c
j -= 1
c = r // 10
result[l] = r % 10
l -= 1
if c != 0:
new_result = [0 for j in range(len(result) + 1)]
t = len(new_result) - 1
while t > 0:
new_result[t] = result[t - 1]
t -= 1
new_result[0] = c
return new_result
return result
arr1 = [9, 9, 9, 9, 9, 9, 9]
arr2 = [1, 6, 8, 2, 6, 7]
result = add(arr1, arr2)
print(result)