Ice Cream Sandwich

An ice cream sandwich is a string that is formed by two identical ends and a different middle.

Some examples of ice cream sandwiches:

"AABBBAA"

"3&&3"

"yyyyymmmmmmmmyyyyy"

"hhhhhhhhmhhhhhhhh"

Notice how left and right ends of the sandwich are identical in both length and in repeating character). The middle section is distinctly different.

Not ice cream sandwiches:

"BBBBB"
// You can't have just plain icecream.

"AAACCCAA"
// You can't have unequal sandwich ends.

"AACDCAA"
// You can't have more than one filling.

"A"
// You can't have fewer than 3 characters.

Write a function that returns True if a string is an ice cream sandwich and False otherwise.

Examples

is_icecream_sandwich("CDC") ➞ True

is_icecream_sandwich("AAABB") ➞ False

is_icecream_sandwich("AA") ➞ False

Notes

An ice cream sandwich must have a minimum length of 3 characters, and at least two of these characters must be distinct (you can't only have the filling!).