#include <bits/stdc++.h>
using namespace std;

class input {

private:

    FILE* fin;
    const int sz = 10000;
    char* buff, c;
    int p;

    char read()
    {
        if (p == sz)
        {
            fread(buff, 1, sz, fin);
            p = 0;
            return buff[p++];
        }
        else
            return buff[p++];
    }

public:
    
    input(const char* name)
    {
        c = '-';
        buff = new char[sz];
        p = sz;
        fin = fopen(name, "r");
    }

    void close()
    {
        fclose(fin);
    }

    void open(const char* name)
    {
        c = '-';
        p = sz;
        fin = fopen(name, "r");
    }

    input& operator >> (int& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;
        int sng = 1;

        if (c == '-')
            sng = -1, c = read();

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        n *= sng;

        return *this;
    }

    input& operator >> (long long& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;
        int sng = 1;

        if (c == '-')
            sng = -1, c = read();

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        n *= sng;

        return *this;
    }

    input& operator >> (unsigned long long& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;
        int sng = 1;

        if (c == '-')
            sng = -1, c = read();

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        n *= sng;

        return *this;
    }

    input& operator >> (char& ch)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        ch = c;

        return *this;
    }

    input& operator >> (string& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = "";

        while (c != ' ' && c != '\n' && c != '\0')
            n += c, c = read();

        return *this;
    }

    input& operator >> (double& n)
    {
        c = read();

        while (c == ' ' || c == '\n')
            c = read();

        n = 0;

        while (isdigit(c))
            n = n * 10 + (c - '0'), c = read();

        if (c != '.')
            return *this;

        c = read();

        double p10 = 10;

        while (isdigit(c))
            n = n + double(c - '0') / p10, c = read(), p10 *= 10;

        return *this;
    }

    void getline(string& s)
    {
        s = "";

        c = read();

        while (c == ' ')
            c = read();

        while (c != '\n')
            s += c, c = read();
    }
};
class output {

private:
    FILE* fout;
    const int sz = 10000;
    char* buff;
    int p;

    void write(char ch)
    {
        if (p == sz)
        {
            fwrite(buff, 1, sz, fout);
            p = 0;
            buff[p++] = ch;
        }
        else
            buff[p++] = ch;
    }

public:

    output(const char* name)
    {
        buff = new char[sz];
        p = 0;
        fout = fopen(name, "w");
    }

    ~output()
    {
        fwrite(buff, 1, p, fout);
    }

    output& operator << (int n)
    {
        if (n < 0)
            write('-'), n *= -1;

        if (n == 0)
        {
            write(n + '0');
            return *this;
        }

        if (n / 10 != 0)
            *this << (n / 10);

        write(('0' + (n % 10)));

        return *this;
    }

    output& operator << (long long n)
    {
        if (n < 0)
        {
            write('-');
            n *= -1;
        }

        if (n < 10)
        {
            write(n + '0');
            return *this;
        }

        *this << (n / 10);
        write((n % 10) + '0');

        return *this;
    }

    output& operator << (unsigned long long n)
    {
        if (n < 0)
        {
            write('-');
            n *= -1;
        }

        if (n < 10)
        {
            write(n + '0');
            return *this;
        }

        *this << (n / 10);
        write((n % 10) + '0');

        return *this;
    }

    output& operator << (char c)
    {
        write(c);
        return *this;
    }

    void precision(double n, int x)
    {
        *this << int(n);

        if (!x)
            return;

        write('.');

        n -= int(n);
        n *= 10;

        for (int i = 1; i <= x; i++)
        {
            *this << int(n);
            n -= int(n);
            n *= 10;
        }
    }

    output& operator << (string n)
    {
        for (auto i : n)
            write(i);
        return *this;
    }
};

input fin("fractii.in");
output fout("fractii.out");

int p[172], k;
bitset <1021> f;

void prime()
{
    int r = sqrt(1020);

    for (int i = 2; i <= r; i++)
    {
        if (f[i])
            continue;

        int j = i + i;

        while (j <= 1020)
            f[j] = 1, j += i;

        p[++k] = i;
    }

    for (int i = r + 1; i <= 1020; i++)
        if (!f[i])
            p[++k] = i;
}

int main()
{
    prime();

    int n;
    fin >> n;

    long long r = 1;

    for (int i = 2; i <= n; i++)
    {
        int x = i;
        int d = 1;
        int a = i;

        do
        {
            bool ok = 0;

            while (x % p[d] == 0)
                x /= p[d], ok = 1;

            if (ok)
                a = a * (p[d] - 1) / p[d];

            d++;

            if (x > 1 && p[d] * p[d] > x)
            {
                a = a * (x - 1) / x;
                break;
            }

        } while (x > 1);

        r += 2 * a;
    }

    fout << r;

    return 0;
}