//Do not declare variable marks.
//Write your code below this line.

if(marks>90)
    console.log('AA');
else if(marks>80)
    console.log('AB');
else if(marks>70)
    console.log('BB');
else if(marks>60)
    console.log('BC');
else if(marks>50)
    console.log('CC');
else if(marks>40)
    console.log('CD');
else if(marks>30)
    console.log('DD');
else
    console.log('FF');