Competitions

# Two identical digits

Four-digit number is given. Determine whether it contains exactly two different digits, each of these digits must occur twice. For example, the numbers 2727 and 6677 satisfy this condition.

#### Input

One four-digit number.

#### Output

Print "YES" if the number satisfies the specified condition, and "NO" otherwise.

Time limit 1 second
Memory limit 128 MiB
Input example #1
2323

Output example #1
YES

Input example #2
2224

Output example #2
NO