//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");