You are given a positive integer n greater or equal to 2. For every pair of integers a and b (2 ≤ |a|, |b| ≤ n), you can transform a into b if and only if there exists an integer x such that 1 < |x| and (a ⋅ x = b or b ⋅ x = a), where |x| denotes the absolute value of x.

After such a transformation, your score increases by |x| points and you are not allowed to transform a into b nor b into a anymore.

Initially, you have a score of 0. You can start at any integer and transform it as many times as you like. What is the maximum score you can achieve?

Input

A single line contains a single integer n (2 ≤ n ≤ 100 000) — the given integer described above.

Output

Print an only integer — the maximum score that can be achieved with the transformations. If it is not possible to perform even a single transformation for all possible starting integers, print 0.

Examples

Input

4


Output

8

Input

6


Output

28

Input

2


Output

0

Note

In the first example, the transformations are 2 → 4 → (-2) → (-4) → 2.

In the third example, it is impossible to perform even a single transformation.
import java.io.*;
import java.util.*;
import java.util.function.Function;

public class Main {

    static int N;

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        N = sc.nextInt();

        System.out.println(solve());
    }

    static long solve() {
        long ans = 0;
        for (int i = 2; i <= N; i++) {
            int j = i + i;
            while(j <= N) {
                // debug(i, j);
                ans += j / i * 4;
                j += i;
            }
        }
        return ans;
    }

    static class Eratos {

        static int[] mkSqrtPrimes(long n) {
            long root_L = (long)Math.sqrt(n);
            if( root_L > 10_000_000 ) throw new IllegalArgumentException("too big : " + n);
            int root = (int)root_L;
            boolean[] sieve = new boolean[root+1];
            Arrays.fill(sieve, true);
            sieve[0] = false;
            sieve[1] = false;

            for (int i = 2; i <= root; i++) {
                if( sieve[i] ) {
                    for (int d = 2; d*i <= root; d++) {
                        sieve[i*d] = false;
                    }
                }
            }

            int cnt = 0;
            for (boolean prime : sieve) {
                if( prime ) cnt++;
            }
            int[] primes = new int[cnt];
            int idx = 0;
            for (int num = 2; num < sieve.length; num++) {
                if( sieve[num] ) {
                    primes[idx++] = num;
                }
            }
            return primes;
        }

        static int factorSize(long n) {
            // 6: 2 * 3 * 5 * 7 * 11 * 13 = 30030
            // 7: 2 * 3 * 5 * 7 * 11 * 13 * 17 = 510510
            // 8: 2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 = 9699690
            // 9: 2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 = 223_092_870
            // 10: 2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 * 29 = 6_469_693_230
            // 11: 2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 * 29 * 31 = 200_560_490_130
            if( n <= 2*3*5*7*11*13 ) {
                return 6;
            } else if( n <= 2*3*5*7*11*13*17 ) {
                return 7;
            } else if( n <= 2L*3*5*7*11*13*17*19 ) {
                return 8;
            } else if( n <= 2L*3*5*7*11*13*17*19*23 ) {
                return 9;
            } else if( n <= 2L*3*5*7*11*13*17*19*23*29 ) {
                return 10;
            } else if( n <= 2L*3*5*7*11*13*17*19*23*29*31 ) {
                return 11;
            } else {
                return 12;
            }
        }

        long n;
        int[] sqrtPrimes;
        int factorSize;

        // cache
        long[] factors;
        long[][] factorCnts;

        Eratos(long n) {
            this.n = n;
            this.sqrtPrimes = mkSqrtPrimes(n);
            this.factorSize = factorSize(n);
            this.factors = new long[this.factorSize];
            this.factorCnts = new long[this.factorSize][2];
        }

        long[] enumUniqFactors(long n) {
            Arrays.fill(factors, 0);
            int i = 0;
            for (int p : sqrtPrimes) {
                if( n % p == 0 ) {
                    factors[i++] = p;
                    n /= p;
                    while( n % p == 0 ) {
                        n /= p;
                    }
                }
            }
            if( n != 1 ) {
                factors[i++] = n;
            }
            return Arrays.copyOf(factors, i);
        }

        long[][] enumFactorCounts(long n) {
            for (long[] fc : factorCnts) {
                fc[0] = 0;
                fc[1] = 0;
            }
            int i = 0;
            for (int p : sqrtPrimes) {
                if( n < p ) break;

                int cnt = 0;
                while( n % p == 0 ) {
                    n/=p;
                    cnt++;
                }
                if( cnt > 0 ) {
                    factorCnts[i][0] = p;
                    factorCnts[i][1] = cnt;
                    i++;
                }
            }
            if( n != 1 ) {
                factorCnts[i][0] = n;
                factorCnts[i][1] = 1;
                i++;
            }
            return Arrays.copyOf(factorCnts, i);
        }

        Map<Long, Integer> mapFactorCounts(long n) {
            long[][] arr = enumFactorCounts(n);
            Map<Long, Integer> map = new HashMap<>();
            for (long[] fc : arr) {
                map.put(fc[0], (int)fc[1]);
            }
            return map;
        }
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
    }

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}
