#include using namespace std; // using mint = long double; // using mint = modint998244353; // using mint = modint1000000007; typedef long long ll; typedef pair P; typedef pair T; typedef pair> Pd; const ll INF = 1e18; const ll fact_table = 320000; priority_queue pql; priority_queue

pqp; // big priority queue priority_queue, greater> pqls; priority_queue, greater

> pqps; // small priority queue // top pop ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1}; ll dy[8] = {0, 1, 0, -1, -1, 1, 1, -1}; //↓,→,↑,← #define p(x) cout << x << "\n"; #define el cout << "\n"; #define pe(x) cout << x << " "; #define ps(x) cout << fixed << setprecision(25) << x << endl; #define pu(x) cout << (x); #define pb push_back #define lb lower_bound #define ub upper_bound #define pc(x) cout << x << ","; #define rep(i, n) for (ll i = 0; i < (n); i++) #define rep2(i, a, b) for (ll i = a; i <= (b); i++) #define rep3(i, a, b) for (ll i = a; i >= (b); i--) #define all(c) begin(c), end(c) #define sorti(v) sort(all(v)) #define sortd(v) \ sort(all(v)); \ reverse(all(v)); #define SUM(v) accumulate(all(v), 0LL) #define MIN(v) *min_element(all(v)) #define MAX(v) *max_element(all(v)) typedef vector vec; typedef vector> mat; // vec v(n) -> 長さnのベクトルを宣言 // mat dp(h, vec(w)) -> h * w の行列を宣言 const ll mod = 1000000007ll; // const ll mod = 998244353ll; ll mypow(ll a, ll b, ll m = mod) { ll x = 1; while (b) { while (!(b & 1)) { (a *= a) %= m; b >>= 1; } (x *= a) %= m; b--; } return x; } vec rv(ll read) { vec res(read); for (int i = 0; i < read; i++) { cin >> res[i]; } return res; } /* ll fact[fact_table + 5], rfact[fact_table + 5]; void c3_init() { fact[0] = rfact[0] = 1; for (ll i = 1; i <= fact_table; i++) { fact[i] = (fact[i - 1] * i) % mod; } rfact[fact_table] = mypow(fact[fact_table], mod - 2, mod); for (ll i = fact_table; i >= 1; i--) { rfact[i - 1] = rfact[i] * i; rfact[i - 1] %= mod; } return; } ll c3(ll n, ll r) { return (((fact[n] * rfact[r]) % mod) * rfact[n - r]) % mod; } */ bool icpc = false; bool multicase = false; ll n; ll spf[50000005]; ll squ[50000005]; ll divu[50000005]; bool solve() { cin >> n; for (int i = 1; i <= n; i++) { spf[i] = i; squ[i] = i; divu[i] = 1; } for (int i = 2; i * i <= n; i++) { if (spf[i] == i) { for (int j = i * i; j <= n; j += i) { if (spf[j] == j) { spf[j] = i; } } } } ll sum = 0; for (int i = 1; i <= n; i++) { ll s = i; ll b = s / spf[s]; if (squ[b] % spf[s] == 0) { squ[i] = squ[b] / spf[s]; divu[i] = divu[b] * spf[s]; } else { squ[i] = squ[b] * spf[s]; divu[i] = divu[b]; } sum += divu[i]; } sum = sum * 2 - n; p(sum); return true; } /* */ int main() { // ios::sync_with_stdio(false); // cin.tie(nullptr); if (icpc) { while (solve()) ; return 0; } ll q, testcase = 1; if (multicase) { cin >> q; } else { q = 1; } while (q--) { // cout << "Case #" << testcase << ": "; solve(); testcase++; } // solve(); return 0; }