# [Japt](https://github.com/ETHproductions/japt), <s>12</s> <s>11</s> 10 bytes

Takes input as an array of digits.

    k@¬èX ÉÃrw

[Test it](http://ethproductions.github.io/japt/?v=1.4.5&code=a0Cs6FggycNydw==&input=WzEsOSw0LDgsNywxLDAsNCw5LDhd)

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## Explanation
         :Implicit input of array U.
    k    :Filter the array to the elements that return false when...
    @    :Passed through a function that...
    ¬    :Joins U to a string and...
    èX   :Counts the number of times the current element (X) appears in the string...
    É    :Minus 1.
         :(The count of unique digits will be 1, 1-1=0, 0=false)
    Ã    :End function.
    r    :Reduce by...
    w    :Getting the greater of the current element and the current value.
         :Implicit output of resulting single digit integer.