//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 {
console.log("FF");}