اللغز الأول

function ex1() {
        let n = parseInt(prompt("number of classes: "));
        console.log(n);
        let s1=0, s2=0;
        for(let i=0;i<n;i++){
            let note, coef;
            [note, coef] = prompt(i+1+") note,coef").split(",");
            console.log(i+1+") note,coef: "+note+", "+coef);
            s1 += parseFloat(note)*parseInt(coef);
            s2 += parseInt(coef);
        }
        let average = s1/s2;
        console.log("average: "+average);
    }