#include using namespace std; vector psieve(int n) { vector pr(n); for (int i = 2; i < n; i++) pr[i] = true; for (int i = 2; i * i < n; i++) { if (!pr[i]) continue; for (int j = i * i; j < n; j += i) pr[j] = false; } return pr; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); int n; cin >> n; auto pr = psieve(3 * n + 1); vector p, q; for (int i = 0; i <= n; i++) if (pr[i]) p.push_back(i); for (int i = 0; i <= 3 * n; i++) if (pr[i]) q.push_back(i); vector suff(3 * n + 1); for (int x: q) { for (int y: p) { if (x - y < 0) break; suff[x - y]++; } } long long ret = 0; // a + b = x(prime) - c for (int i = 0; i < p.size(); i++) { // b // remove c = b for (int x: q) if (x - p[i] > 0) --suff[x - p[i]]; for (int j = 0; j < i; j++) { // a ret += suff[p[j] + p[i]]; } } cout << ret << endl; return 0; }