r a b c
  | c > a && c > b = c == a + b
  | a > c && a > b = a == b + c
  | b > c && b > a = b == a + c
  | otherwise = False
r a b c
  | c > a && c > b = c == a + b
  | a > c && a > b = a == b + c
  | b > c && b > a = b == a + c
  | otherwise = False
r a b c
  | c > a && c > b = c == a + b
  | a > c && a > b = a == b + c
  | b > c && b > a = b == a + c
  | otherwise = False