Problem p02624 (C++) — buggy submission, verdict: Time Limit Exceeded

#pragma region header
#include <bits/stdc++.h>
#define int long long
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define mp make_pair
#define mt make_tuple
#define rep1(i, n) for (decltype(+n) i = 0; i < (n); i++)
#define rrep1(i, n) for (auto i = n - 1; i > static_cast<decltype(i)>(-1); i--)
#define rep2(i, a, b) for (auto i = (a); i < (b); i++)
#define rrep2(i, a, b) for (auto i = b - 1; i >= a; i--)
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep(...) GET_MACRO(__VA_ARGS__, rrep2, rrep1)(__VA_ARGS__)
#define each(i, a) for (auto &&i : (a))
using namespace std;

using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using vvs = vector<vs>;
using vd = vector<ld>;
using vvd = vector<vd>;
using vb = vector<bool>;
using vvb = vector<vb>;
using pii = pair<int, int>;
using vp = vector<pii>;
using vvp = vector<vp>;
using mii = map<int, int>;
using vm = vector<mii>;
using vvm = vector<vm>;

constexpr int INF = 1e18;
constexpr int MOD = 1e9 + 7;

template <class T> void SORT(T &a) { stable_sort(all(a)); }
template <class T> void RSORT(T &a) { stable_sort(rall(a)); }
template <class T> void rev(T &a) { reverse(rall(a)); }
template <class T> void uniq(T &a) { a.erase(unique(all(a)), end(a)); }
template <class T> auto min_of(T a) { return *min_element(all(a)); }
template <class T> auto max_of(T a) { return *max_element(all(a)); }
template <class T> int sum_of(T a) { return accumulate(all(a), 0ll); }
template <class T, class U> auto sum_of(T a, U init) {
  return accumulate(all(a), init);
}
template <class T, class U> int count_of(T a, U i) { return count(all(a), i); }
template <class T, class U> int lower_index(T a, U i) {
  return lower_bound(all(a), i) - begin(a);
} // use member func for set
template <class T, class U> int upper_index(T a, U i) {
  return upper_bound(all(a), i) - begin(a);
}
template <class T, class U> bool binary(T a, U i) {
  return binary_search(all(a), i);
}
template <class T, class U> bool has(T a, U i) {
  return find(all(a), i) != end(a);
}
template <class T> int sz(T a) { return a.size(); };

template <class T> void COUT(T x) { cout << x << endl; }
template <class T, class U> void COUT(T x, U y) {
  cout << x << ' ' << y << endl;
}
template <class T, class U, class V> void COUT(T x, U y, V z) {
  cout << x << ' ' << y << ' ' << z << endl;
}
template <class T> void CSP(T x) { cout << x << ' '; }
template <class T> void CVEC(T v) {
  int c = v.size() - 1;
  for (size_t i = 0; i < c; i++)
    cout << v[i] << ' ';
  if (c > -1)
    cout << v[c];
  cout << endl;
}

template <class T> bool amin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool amax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

int ceil_div(int x, int y) { return (x - 1) / y + 1; }

#pragma endregion header

void solve(int n) {
  int ans = 0;
  rep(i, 1, n + 1) ans += n / i * (n / i + 1) / 2 * i;
  COUT(ans);
}

#pragma region main
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << fixed << setprecision(15);

  int n;
  cin >> n;
  solve(n);
}
#pragma endregion main


Error: TLE

Fixed submission:

#pragma region header
#include <bits/stdc++.h>
#define int long long
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define mp make_pair
#define mt make_tuple
#define rep1(i, n) for (decltype(+n) i = 0; i < (n); i++)
#define rrep1(i, n) for (auto i = n - 1; i > static_cast<decltype(i)>(-1); i--)
#define rep2(i, a, b) for (auto i = (a); i < (b); i++)
#define rrep2(i, a, b) for (auto i = b - 1; i >= a; i--)
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#define rrep(...) GET_MACRO(__VA_ARGS__, rrep2, rrep1)(__VA_ARGS__)
#define each(i, a) for (auto &&i : (a))
using namespace std;

using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using vvs = vector<vs>;
using vd = vector<ld>;
using vvd = vector<vd>;
using vb = vector<bool>;
using vvb = vector<vb>;
using pii = pair<int, int>;
using vp = vector<pii>;
using vvp = vector<vp>;
using mii = map<int, int>;
using vm = vector<mii>;
using vvm = vector<vm>;

constexpr int INF = 1e18;
constexpr int MOD = 1e9 + 7;

template <class T> void SORT(T &a) { stable_sort(all(a)); }
template <class T> void RSORT(T &a) { stable_sort(rall(a)); }
template <class T> void rev(T &a) { reverse(rall(a)); }
template <class T> void uniq(T &a) { a.erase(unique(all(a)), end(a)); }
template <class T> auto min_of(T a) { return *min_element(all(a)); }
template <class T> auto max_of(T a) { return *max_element(all(a)); }
template <class T> int sum_of(T a) { return accumulate(all(a), 0ll); }
template <class T, class U> auto sum_of(T a, U init) {
  return accumulate(all(a), init);
}
template <class T, class U> int count_of(T a, U i) { return count(all(a), i); }
template <class T, class U> int lower_index(T a, U i) {
  return lower_bound(all(a), i) - begin(a);
} // use member func for set
template <class T, class U> int upper_index(T a, U i) {
  return upper_bound(all(a), i) - begin(a);
}
template <class T, class U> bool binary(T a, U i) {
  return binary_search(all(a), i);
}
template <class T, class U> bool has(T a, U i) {
  return find(all(a), i) != end(a);
}
template <class T> int sz(T a) { return a.size(); };

template <class T> void COUT(T x) { cout << x << endl; }
template <class T, class U> void COUT(T x, U y) {
  cout << x << ' ' << y << endl;
}
template <class T, class U, class V> void COUT(T x, U y, V z) {
  cout << x << ' ' << y << ' ' << z << endl;
}
template <class T> void CSP(T x) { cout << x << ' '; }
template <class T> void CVEC(T v) {
  int c = v.size() - 1;
  for (size_t i = 0; i < c; i++)
    cout << v[i] << ' ';
  if (c > -1)
    cout << v[c];
  cout << endl;
}

template <class T> bool amin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool amax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

int ceil_div(int x, int y) { return (x - 1) / y + 1; }

#pragma endregion header

vi memo;
vb prime;
vi ps;
void prime_table(int n) {
  prime = vb(n + 1, true);
  if (n >= 0)
    prime[0] = false;
  if (n >= 1)
    prime[1] = false;
  for (int i = 2; i * i <= n; i++) {
    if (!prime[i])
      continue;
    for (int j = i + i; j <= n; j += i) {
      prime[j] = false;
    }
  }
}
int divs(int n) {
  mii ret;
  each(i, ps) {
    if (i * i > n)
      break;
    while (n % i == 0) {
      ret[i]++;
      n /= i;
    }
  }
  if (n != 1)
    ret[n]++;
  int s = 1;
  each(p, ret) s *= p.second + 1;
  return s;
}

void solve(int n) {
  int ans = 0;
  memo = vi(n + 1);
  prime_table(n);
  for (int i = 2; i * i <= n; i++)
    if (prime[i])
      ps.push_back(i);
  rep(i, 1, n + 1) ans += divs(i) * i;
  COUT(ans);
}

#pragma region main
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout << fixed << setprecision(15);

  int n;
  cin >> n;
  solve(n);
}
#pragma endregion main