Problem p02624 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;

// TEMPLATE
#define pb push_back
#define mp make_pair
#define ll long long
#define ld long double
#define pii pair<ll, ll>
#define piii pair<ll, pii>
#define F first
#define S second

#define newline printf("\n")
#define minusone printf("-1\n")
#define zeroo printf("0\n")
#define scl1(a) scanf("%lld", &a)
#define scl2(a, b) scanf("%lld %lld", &a, &b)
#define scl3(a, b, c) scanf("%lld %lld %lld", &a, &b, &c)
#define prl1(a) printf("%lld\n", a)
#define prl2(a, b) printf("%lld %lld\n", a, b)
#define ssl1(s) scanf(" %[^\n]", s)
#define scd1(a) scanf("%lf", &a)
#define scd2(a, b) scanf("%lf %lf", &a, &b)
#define prd(a) printf("%lf\n", a)
#define prld(a) printf("%Lf\n", a)
#define prcase(cs) printf("Case %lld: ", cs)
#define cin1(a) cin >> a
#define cin2(a, b) cin >> a >> b
#define cin3(a, b, c) cin >> a >> b >> c
#define cin4(a, b, c, d) cin >> a >> b >> c >> d
#define cot1(a) cout << a << "\n"
#define cot2(a, b) cout << a << " " << b << "\n"
#define cot3(a, b, c) cout << a << " " << b << " " << c << "\n"
#define cot4(a, b, c, d) cout << a << " " << b << " " << c << " " << d << "\n"
#define cotline cout << "\n"
#define cotminus cout << "-1\n"
#define cot0 cout << "0\n"
#define cotyes cout << "YES\n"
#define cotno cout << "NO\n"
#define cotcase(cs) cout << "Case " << cs << ": "

#define reversed(s) reverse(s.begin(), s.end())
#define asort(s) sort(s.begin(), s.end())
#define dsort(s) sort(s.rbegin(), s.rend())
#define all(s) s.begin(), s.end()
#define uniq(s) s.resize(distance(s.begin(), unique(s.begin(), s.end())))
#define found(s, x) s.find(x) != s.end()

#define for0(i, n) for (i = 0; i < n; i++)
#define for1(i, n) for (i = 1; i <= n; i++)
#define fora(i, a, b) for (i = a; i <= b; i++)
#define forb(i, b, a) for (i = b; i >= a; i--)
#define fori(it, s) for (auto it = s.begin(); it != s.end(); it++)

#define FR                                                                     \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL)
#define ms(a, x) memset(a, x, sizeof a)
#define bitcount(n) __builtin_popcountll(n)

// #define pi              3.1415926536
#define pi acos(-1)

const ll INF = LLONG_MAX;
const ll SZ = 4e5 + 5;
const ll mod = 1e9 + 7;

ll n;
unsigned ll a[SZ];
// ll b[SZ];

int main() {
  FR;
  ll cs = 0, tc = 1, x, y, z, i, j, k, g, p, q, ans = 0, sum = 0, t = 0;
  //    ll a, b, d;
  string s, s1, s2;

  cin1(n);

  unsigned ll c = 0;
  for1(i, n) {
    for (j = i; j <= n; j += i) {
      a[j]++;
    }
  }

  for1(i, n) { c += (a[i] * i); }

  cot1(c);

  return 0;
}


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

// TEMPLATE
#define pb push_back
#define mp make_pair
#define ll long long
#define ld long double
#define pii pair<ll, ll>
#define piii pair<ll, pii>
#define F first
#define S second

#define newline printf("\n")
#define minusone printf("-1\n")
#define zeroo printf("0\n")
#define scl1(a) scanf("%lld", &a)
#define scl2(a, b) scanf("%lld %lld", &a, &b)
#define scl3(a, b, c) scanf("%lld %lld %lld", &a, &b, &c)
#define prl1(a) printf("%lld\n", a)
#define prl2(a, b) printf("%lld %lld\n", a, b)
#define ssl1(s) scanf(" %[^\n]", s)
#define scd1(a) scanf("%lf", &a)
#define scd2(a, b) scanf("%lf %lf", &a, &b)
#define prd(a) printf("%lf\n", a)
#define prld(a) printf("%Lf\n", a)
#define prcase(cs) printf("Case %lld: ", cs)
#define cin1(a) cin >> a
#define cin2(a, b) cin >> a >> b
#define cin3(a, b, c) cin >> a >> b >> c
#define cin4(a, b, c, d) cin >> a >> b >> c >> d
#define cot1(a) cout << a << "\n"
#define cot2(a, b) cout << a << " " << b << "\n"
#define cot3(a, b, c) cout << a << " " << b << " " << c << "\n"
#define cot4(a, b, c, d) cout << a << " " << b << " " << c << " " << d << "\n"
#define cotline cout << "\n"
#define cotminus cout << "-1\n"
#define cot0 cout << "0\n"
#define cotyes cout << "YES\n"
#define cotno cout << "NO\n"
#define cotcase(cs) cout << "Case " << cs << ": "

#define reversed(s) reverse(s.begin(), s.end())
#define asort(s) sort(s.begin(), s.end())
#define dsort(s) sort(s.rbegin(), s.rend())
#define all(s) s.begin(), s.end()
#define uniq(s) s.resize(distance(s.begin(), unique(s.begin(), s.end())))
#define found(s, x) s.find(x) != s.end()

#define for0(i, n) for (i = 0; i < n; i++)
#define for1(i, n) for (i = 1; i <= n; i++)
#define fora(i, a, b) for (i = a; i <= b; i++)
#define forb(i, b, a) for (i = b; i >= a; i--)
#define fori(it, s) for (auto it = s.begin(); it != s.end(); it++)

#define FR                                                                     \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL)
#define ms(a, x) memset(a, x, sizeof a)
#define bitcount(n) __builtin_popcountll(n)

// #define pi              3.1415926536
#define pi acos(-1)

const ll INF = LLONG_MAX;
const ll SZ = 1e7 + 5;
const ll mod = 1e9 + 7;

ll n;
unsigned ll a[SZ];
// ll b[SZ];

int main() {
  FR;
  ll cs = 0, tc = 1, x, y, z, i, j, k, g, p, q, ans = 0, sum = 0, t = 0;
  //    ll a, b, d;
  string s, s1, s2;

  cin1(n);

  unsigned ll c = 0;
  for1(i, n) {
    for (j = i; j <= n; j += i) {
      a[j]++;
    }
  }

  for1(i, n) { c += (a[i] * i); }

  cot1(c);

  return 0;
}