function Main(input){
    input=input.split("\n");  //ここまで必須
    var num=new Array();
    var yaku=new Array();

    for (i=1;i<parseInt(input[0])+1;i++){
        num.push(i);
        var kosu=0;
        for(j=1;j<parseInt(i)+1;j++){
            if (i%j==0){kosu=kosu+1}
        }
        yaku.push(kosu);
    }
    var result=0;
    for (k=0;k<input[0];k++){
        result=result+parseInt(num[k])*parseInt(yaku[k])
   
    }
    console.log(result);
}
Main(require("fs").readFileSync("/dev/stdin","utf8"));