//Do not declare variable marks.
//Write your code below this line.
if(marks>90)
    {
        console.log('AA');
    }
else if(marks>80||marks<=90)
    {
        console.log('AB');
    }
else if(marks>70||marks<=80)
    {
        console.log('BB');
    }
else if(marks>60||marks<=70)
    {
        console.log('BC');
    }
else if(marks>50||marks<=60)
    {
        console.log('CC');
    }
else if(marks>40||marks<=50)
    {
        console.log('CD');
    }
else if(marks>30||marks<=40)
    {
        console.log('DD');
    }
else if(marks<=30)
    {
        console.log('FF');
    }