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