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

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