const main = args =>{
  const N = Number(args);
  result = 0;
  for(let i=1;i<=N;i++){
    result += i*f(i);
  }
  console.log(result);
}

const f = N =>{
  const iter = Math.floor(Math.sqrt(N));
  let result = 0;
  for(let i=1;i<=iter;i++){
    if(N%i===0){
      result+=2;
    }
  }
  if(iter**2 === N){
    result--;
  }
  return result;
}
 
const split_string = s => {
  return s.split(' ').map(Number);
}
 
main( require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n") );