def octal_to_string(octal):
result = ""
value_letters = [(4,"r"),(2,"w"),(1,"x")]
# Iterate over each of the digits in octal
for odigit in [int(n) for n in str(octal)]:
# Check for each of the permissions values
for value, letter in value_letters:
if odigit >= value:
result += letter
odigit -= value
else:
result += "-"
return result
print(octal_to_string(755)) # should return rwxr-xr-x