function exam (input) {
  let hourOfExam = parseInt(input[0]);
  let minuteOfExam = parseInt(input[1]);
  let hourOfArrival = parseInt(input[2]);
  let minuteOfArrival = parseInt(input[3]);

  let ExamTime = (hourOfExam * 60) + minuteOfExam;
  let ArrivalTime = (hourOfArrival * 60) + minuteOfArrival;

  let diff = ExamTime - ArrivalTime;

  // Case 1: Where student is on time for this exam

  if (diff >= 0) {
    if (diff <= 30) {
      console.log("On Time")
      if (diff <= 30 && diff != 0) {
        console.log(`${diff} minutes before the start`)
      }
    } else if (diff > 30) {

      // Case 2: Where student is early for this exam

      console.log("Early")
      if (diff < 60) {
        console.log(`${diff} minutes before the start`)
      } else {
        let hour = Math.floor(diff / 60);
        let minutes = diff % 60;
        if (minutes <= 9) {
          console.log(`${hour}:0${minutes} hours before the start`)
        } else {
          console.log(`${hour}:${minutes} hours before the start`)
        }
        }
      }
    } else {

      // Case 3: Where student is late for this exam

      console.log("Late")
      let positiveDiff = diff * -1
      if (positiveDiff <= 59) {
        console.log(`${positiveDiff} minutes after the start`)
      } else {
        let hour = Math.floor(positiveDiff / 60);
        let minutes = positiveDiff % 60;
        if (minutes <= 9) {
          console.log(`${hour}:0${minutes} hours after the start`)
        } else {
          console.log(`${hour}:${minutes} hours after the start`)
      }
    }
  }
}