Triangle Classification

Classify three side lengths as invalid, equilateral, isosceles, or scalene. A valid triangle has positive sides, and its two shortest sides must sum to more than its longest side. Equal-to is invalid: it forms a straight line. Use equilateral for three equal sides, isosceles for exactly two, and scalene for three different sides.

Implement triangle_classification(sides).

Input

sides: The three side lengths in any order.

Output

Return one lowercase label: invalid, equilateral, isosceles, or scalene.

制約

Exactly three integer sides, each between −1,000,000,000 and 1,000,000,000. Nonpositive sides are invalid.

例

入力：
sides = [5, 5, 8]

期待される出力：
expected = "isosceles"

入力：
std::vector<long long> sides = {5, 5, 8};

期待される出力：
std::string expected = "isosceles";

入力：
long[] sides = new long[] {5, 5, 8};

期待される出力：
string expected = "isosceles";

入力：
sides = [1, 2, 3]

期待される出力：
expected = "invalid"

入力：
std::vector<long long> sides = {1, 2, 3};

期待される出力：
std::string expected = "invalid";

入力：
long[] sides = new long[] {1, 2, 3};

期待される出力：
string expected = "invalid";

参考資料

この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。

• Exercism: Triangle