Given a string and two characters, Find the minimum distance between two given characters in the string.
String: "Hello world"
Character 1: 'o'
Character 2: 'l'
Minimum distance is 1
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Given a string and two characters, Find the minimum distance between two given characters in the string.

### Response:
Minimum distance is 1