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Challenge

Compactify a long list of numbers by replacing consecutive runs with ranges.

Example

Input

1, 2, 3, 4, 7, 8, 10, 12, 13, 14, 15

Output:

1 - 4, 7, 8, 10, 12 - 15
Note that ranges of two numbers should be left as is. (7, 8; not 7 - 8)

Rules

You can accept a list of integers (or equivalent datatype) as a method parameter, from the commandline, or from standard in. (pick whichever option results in shorter code)
You can output a list of strings by printing them, or by returning either a single string or set of strings.

Reference Implementation

(C#)

IEnumerable<string> Sample(IList<int> input) {
    for (int i = 0; i < input.Count; ) {
        var start = input[i];
        int size = 1;
        while (++i < input.Count && input[i] == start + size)
            size++;

        if (size == 1)
            yield return start.ToString();
        else if (size == 2) {
            yield return start.ToString();
            yield return (start + 1).ToString();
        } else if (size > 2)
            yield return start + " - " + (start + size - 1);
    }
}