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

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