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

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

#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define repp(i, n, m) for (int(i) = (n); (i) < (m); (i)++)
#define repn(i, n) for (int(i) = 1; (i) <= (n); (i)++)
#define repr(i, n) for (int(i) = (n - 1); (i) >= 0; (i)--)
#define all(x) (x).begin(), (x).end()
#define lint long long
#define ulint unsigned long long
#define ldou long double
#define fi first
#define se second
#define setpre(x) std::cout << fixed << setprecision(x)
#define ii(x)                                                                  \\
  int x;                                                                       \\
  cin >> (x)
#define ii2(x, y)                                                              \\
  int x, y;                                                                    \\
  cin >> (x) >> (y)
#define ii3(x, y, z)                                                           \\
  int x, y, z;                                                                 \\
  cin >> (x) >> (y) >> (z)
#define out(x) cout << (x) << endl
#define outs(x) cout << (x) << " "
#define yn(x) cout << ((x) ? ("Yes") : ("No")) << endl
#define YN(x) cout << ((x) ? ("YES") : ("NO")) << endl
#define bit_c(x) __builtin_popcountll(x)

inline void logger() { std::cout << " [LOGGER] " << endl; }
template <typename A, typename... B> void logger(const A &a, const B &...b) {
  cout << a << " , ";
  logger(b...);
}

typedef pair<lint, lint> P;
const lint MOD = 1000000007;
const lint MOD9 = 998244353;
const lint INF = MOD * MOD;
const int MAX = 2000005;

/* ...o(^-^)o... */

int main() {
  lint n;
  cin >> n;
  lint ans = 0;
  repn(k, n) {
    lint l = n / k;
    ans += k * (l * (l + 1) / 2);
  }
  out(ans);
}

Error: TLE

Fixed submission:

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

#define rep(i, n) for (int(i) = 0; (i) < (n); (i)++)
#define repp(i, n, m) for (int(i) = (n); (i) < (m); (i)++)
#define repn(i, n) for (int(i) = 1; (i) <= (n); (i)++)
#define repr(i, n) for (int(i) = (n - 1); (i) >= 0; (i)--)
#define all(x) (x).begin(), (x).end()
#define lint long long
#define ulint unsigned long long
#define ldou long double
#define fi first
#define se second
#define setpre(x) std::cout << fixed << setprecision(x)
#define ii(x)                                                                  \\
  int x;                                                                       \\
  cin >> (x)
#define ii2(x, y)                                                              \\
  int x, y;                                                                    \\
  cin >> (x) >> (y)
#define ii3(x, y, z)                                                           \\
  int x, y, z;                                                                 \\
  cin >> (x) >> (y) >> (z)
#define out(x) cout << (x) << endl
#define outs(x) cout << (x) << " "
#define yn(x) cout << ((x) ? ("Yes") : ("No")) << endl
#define YN(x) cout << ((x) ? ("YES") : ("NO")) << endl
#define bit_c(x) __builtin_popcountll(x)

inline void logger() { std::cout << " [LOGGER] " << endl; }
template <typename A, typename... B> void logger(const A &a, const B &...b) {
  cout << a << " , ";
  logger(b...);
}

typedef pair<lint, lint> P;
const lint MOD = 1000000007;
const lint MOD9 = 998244353;
const lint INF = MOD * MOD;
const int MAX = 2000005;

/* ...o(^-^)o... */

map<int, int> prime_factorization(int x) {
  map<int, int> fac;
  for (int k = 2; k * k <= x; k++) {
    while (x % k == 0) {
      fac[k]++;
      x /= k;
    }
  }
  if (x != 1)
    fac[x]++;
  return fac;
}

lint solve(int k) {
  map<int, int> mp = prime_factorization(k);

  lint count = 1;
  for (auto p : mp)
    count *= (lint)(p.se + 1);

  return count * (lint)k;
}

int main() {
  lint n;
  cin >> n;
  lint ans = 0;
  repn(k, n) { ans += solve(k); }
  out(ans);
}