#include #define rep(i,a,b) for(int i=a;i=b;i--) #define fore(i,a) for(auto &i:a) #define all(x) (x).begin(),(x).end() #pragma GCC optimize ("-O3") using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60; templatebool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b makePrimes(int n) { // [2,n] vector res, pr(n + 1, 1); pr[0] = pr[1] = 0; rep(p, 2, sqrt(n) + 2) if (pr[p]) for (int x = p * 2; x <= n; x += p) pr[x] = 0; rep(p, 2, n + 1) if (pr[p]) res.push_back(p); return res; } /*---------------------------------------------------------------------------------------------------             ∧_∧       ∧_∧  (´<_` )  Welcome to My Coding Space!      ( ´_ゝ`) /  ⌒i     /   \    | |     /   / ̄ ̄ ̄ ̄/  |   __(__ニつ/  _/ .| .|____      \/____/ (u ⊃ ---------------------------------------------------------------------------------------------------*/ int N; ll cnt[301010]; //--------------------------------------------------------------------------------------------------- void _main() { cin >> N; auto vp = makePrimes(N); auto vp2 = makePrimes(N * 3); ll ans = 0; vector va; fore(c, vp) { fore(abc, vp2) if (c < abc) ans += cnt[abc - c]; fore(a, va) cnt[a + c]++; va.push_back(c); } cout << ans << endl; }