function triangleArea(side1, side2, side3) {
  let n =
    (1 / 4) *
    Math.sqrt(
      (side1 + side2 + side3) *
        (side2 + side3 - side1) *
        (side1 + side3 - side2) *
        (side1 + side2 - side3)
    );
  console.log(n);
}
triangleArea(2, 3.5, 4);