//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 
    console.log('FF');