void main() {
  problem();
}

ulong[] generatePrimes(ulong limit)
{
  bool[] PS = new bool[limit + 1];
  PS[] = true;
  PS[0] = false;
  PS[1] = false;
  foreach (i; 2..limit+1) {
    if (PS[i]) {
      auto x = i*2;
      while (x <= limit) {
        PS[x] = false;
        x += i;
      }
    }
  }

  ulong[] primes;
  foreach(i; 2..limit+1) {
    if (PS[i]) primes ~= i;
  }

  return primes;
}
void problem() {
  auto N = scan!ulong;
  auto primes = generatePrimes(N/2);
  auto diviersCount = new long[N + 1];
  diviersCount[] = 2;
  diviersCount[1] = 1;

  void calc(ulong base, ulong[] primes, ulong stack) {
    foreach(i; 0..primes.length) {
      ulong k = base;
      ulong c = 1;
      while(true) {
        k *= primes[i];
        if (k > N) break;

        diviersCount[k] = stack * ++c;
        if (primes.length > 1) calc(k, primes[i+1..$], diviersCount[k]);
      }
    }
  }

  calc(1, primes, 1);

  ulong solve() {
    ulong ans;
    foreach(n; 1..N+1) {
      ans += n * diviersCount[n];
    }
    return ans;
  }

  solve().writeln;
}

// ----------------------------------------------

import std.stdio, std.conv, std.array, std.string, std.algorithm, std.container, std.range, core.stdc.stdlib, std.math, std.typecons, std.numeric;
T[][] combinations(T)(T[] s, in int m) {   if (!m) return [[]];   if (s.empty) return [];   return s[1 .. $].combinations(m - 1).map!(x => s[0] ~ x).array ~ s[1 .. $].combinations(m); }
string scan(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T scan(T)(){ return scan.to!T; }
T[] scan(T)(int n){ return n.iota.map!(i => scan!T()).array; }
void deb(T ...)(T t){ debug writeln(t); }
alias Queue = Tuple!(long, "from", long, "to");

// -----------------------------------------------
