//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<=80)
    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 if (marks<=30)
    console.log("FF");