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Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used.

**Note:**

- All letters in hexadecimal (
`a-f`

) must be in lowercase. - The hexadecimal string must not contain extra leading
`0`

s. If the number is zero, it is represented by a single zero character`'0'`

; otherwise, the first character in the hexadecimal string will not be the zero character. - The given number is guaranteed to fit within the range of a 32-bit signed integer.
- You
**must not use**which converts/formats the number to hex directly.*any*method provided by the library

**Example 1:**

Input: 26 Output: "1a"

**Example 2:**

Input: -1 Output: "ffffffff"

b''