//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');}