//Do not declare variable marks.
//Write your code below this line.
    if (marks>90){
        console.log("AA");
    }else if(marks>80 ||marks<=90){
        console.log("AB");
    }else if(marks>70 || marks<=80){
        console.log('BB');
        
    }else if (marks>60 || marks<=70){
        console.log('BC');
    }else if (marks>50 || marks <=60){
        console.log('CC');
    }else if(marks>40 || marks <=50){
        console.log("CD");
    }else if(marks>30 || marks <=40){
        console.log("DD");
    }else {
        console.log("FF");
    }