function exam(examHr, examMn, arriveHr, arriveMn){
    examHr = Number(examHr);
    examMn = Number(examMn);
    arriveHr = Number(arriveHr);
    arriveMn = Number(arriveMn);
    let totalExamMn = examHr*60 + examMn;
    let totalAriveTime = arriveMn + arriveHr*60;
    let diff = totalExamMn - totalAriveTime;
    let hr = Math.abs(diff/60);
    hr = Math.floor(hr);
    let mn =  Math.abs(diff % 60);
    if(diff === 0 ){
        console.log('On time');
    }else if(diff <= 30 && diff > 0){
        console.log('On time');
        console.log(`${mn} minutes before the start`);
    }
    if(mn < 10){
        mn = `0${mn}`;
    }
     if(diff > 30){
            if(hr >= 1){
                console.log('Early');
                console.log(`${hr}:${mn} hours before the start`);
            }else{
                console.log('Early');
                console.log(`${mn} minutes before the start`);
            }
        }
    else if(diff < 0){
             if(diff < - 60){
                console.log('Late');
                console.log(`${hr}:${mn} hours after the start`);
            }else{
                console.log('Late');
                console.log(`${mn} minutes after the start`);
            }
        }
    }