#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Triangle Project Code.

# Triangle analyzes the lengths of the sides of a triangle
# (represented by a, b and c) and returns the type of triangle.
#
# It returns:
#   'equilateral'  if all sides are equal
#   'isosceles'    if exactly 2 sides are equal
#   'scalene'      if no sides are equal
#
# The tests for this method can be found in
#   about_triangle_project.py
# and
#   about_triangle_project_2.py
#
def triangle(a, b, c):

    if a<=0 or b <=0 or c<=0:
        raise TriangleError

    k1, k2, h = sorted([a, b, c])

    if k1 + k2 <= h:
        raise TriangleError


    if a==b and b==c:
        return "equilateral"

    if a==b or b==c or a==c:
        return "isosceles"

    return "scalene"

# Error class used in part 2.  No need to change this code.
class TriangleError(Exception):
        pass