var Students:[String:Double]=["stud1":100,"stud2":95,"stud3":99,"stud4":55,"stud5":77,"stud6":63,"stud7":49,"stud8":89,"stud9":20,"stud10":67]
var myTuble:(avg:Double,failed:String,underAvg:String,max:Double)
func myFunction(myStudents:[String:Double])->(avg:Double,failed:String,underAvg:String,max:Double)
{
    var sum:Double=0;
    var avg:Double;
    var  failedStudents:String = "";
    var underAvg:String = "";
    var max:Double = 0;
    for item in myStudents
    {
        sum+=item.value;
        if item.value<56
        {
            failedStudents+="\(item.key) ";
        }
        if item.value>max
        {
            max=item.value;
        }
    }
    avg = sum/Double(myStudents.count);
    for item in myStudents
    {
        sum+=item.value;
        if item.value<avg
        {
            underAvg+="\(item.key) ";
        }
    }
    return (avg:avg,failed:failedStudents,underAvg:underAvg,max:max);
}
myTuble=myFunction(myStudents: Students);
print("students average is: \(myTuble.avg) \n ,failed: \(myTuble.failed) \n, under average: \(myTuble.underAvg)\n, the max grade is:\(myTuble.max)");