This question is similar as conversion of number systems, that is base 10 to base 26

```
class Solution(object):
def convertToTitle(self, n):
"""
:type n: int
:rtype: str
"""
i = ("A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z")
k = n
str = ""
while k > 0:
str += i[k%26-1]
if k%26 == 0:
k = k / 26 - 1
else:
k /= 26
return str[::-1]
```