//OPCIÓN 1
function getGrade (s1, s2, s3) {
  avg = (s1+s2+s3)/3;
  if (avg < 60)  return "F";
    else if (avg < 70) return "D";
    else if (avg < 80) return "C";
    else if (avg < 90) return "B";
    else return "A";
}

//OPCIÓN 2
function getGrade(...scores) {
  let avg = scores.reduce((a, b) => a + b, 0) / scores.length;
  
  if (avg < 60)  return "F";
    else if (avg < 70) return "D";
    else if (avg < 80) return "C";
    else if (avg < 90) return "B";
    else return "A";