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

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