Problem p02724 (C++) — buggy submission, verdict: Runtime Error

/*
 KUNAL RAUT (ZUKONIT14)  :- "DO WHAT YOU LIKE!"
 -PICT,PUNE! :)
 */
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int long long
#define ld long double
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define mod 1000000007
#define mod9 1000000009
#define pi 3.1415926535
#define MAXN 100005
#define N 1000001
#define MAX2N 1 * 1000 + 10
#define all(v) v.begin(), v.end()
#define ms(s, n) memset(s, n, sizeof(s))
#define prec(n) fixed << setprecision(n)
#define forci(p, n) for (ll i = p; i < (ll)n; i++)
#define forcj(p, n) for (ll j = p; j < (ll)n; j++)
#define bolt                                                                   \\
  ios_base::sync_with_stdio(0);                                                \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
#define bits(a) __builtin_popcount(a)
#define test                                                                   \\
  ll t;                                                                        \\
  cin >> t;                                                                    \\
  for (ll testi = 1; testi <= t; testi++)
ll zero = 0;
ll one = 1;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return (a / gcd(a, b) * b); }
ll expo(ll x, ll y) {
  ll res = 1;
  x = x % mod;
  while (y > 0) {
    if (y & 1)
      res = (1ll * res * x) % mod;
    y = y >> 1;
    x = (1ll * x * x) % mod;
  }
  return res;
}
ll ncr(ll n, ll r) {
  ll res = 1;
  if (r > n - r)
    r = n - r;
  for (ll i = 0; i < r; i++) {
    res *= n - i;
    res /= i + 1;
  }
  return res;
}
ll max(ll a, ll b) { return (a > b) ? a : b; }
bool prime(ll n) {
  ll i;
  for (i = 2; i <= sqrt(n); i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
bool sortbysec(const pair<ll, ll> &a, const pair<ll, ll> &b) {
  if (a.second == b.second)
    return a.first < b.first;
  return (a.second < b.second);
}
// https://www.youtube.com/watch?v=WTJSt4wP2ME

ll rr[] = {
    0, 1, 1, 1, 0, -1, -1, -1,
};
ll cc[] = {1, 1, 0, -1, -1, -1, 0, 1};

ll a[MAXN], ans[MAXN];

signed main() {
  bolt;
  // #ifndef ONLINE_JUDGE
  //     freopen("input00.txt", "r", stdin);
  //     freopen("output00.txt", "w", stdout);
  // #endif
  ll x;
  cin >> x;
  ll ans = 0;
  ans += 1000 * (x / 500);
  x %= 500;
  ans += (5 * (x / 5));
  cout << ans;
}


Error: WA

Fixed submission:

/*
 KUNAL RAUT (ZUKONIT14)  :- "DO WHAT YOU LIKE!"
 -PICT,PUNE! :)
 */
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int long long
#define ld long double
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define mod 1000000007
#define mod9 1000000009
#define pi 3.1415926535
#define MAXN 100005
#define N 1000001
#define MAX2N 1 * 1000 + 10
#define all(v) v.begin(), v.end()
#define ms(s, n) memset(s, n, sizeof(s))
#define prec(n) fixed << setprecision(n)
#define forci(p, n) for (ll i = p; i < (ll)n; i++)
#define forcj(p, n) for (ll j = p; j < (ll)n; j++)
#define bolt                                                                   \\
  ios_base::sync_with_stdio(0);                                                \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
#define bits(a) __builtin_popcount(a)
#define test                                                                   \\
  ll t;                                                                        \\
  cin >> t;                                                                    \\
  for (ll testi = 1; testi <= t; testi++)
ll zero = 0;
ll one = 1;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return (a / gcd(a, b) * b); }
ll expo(ll x, ll y) {
  ll res = 1;
  x = x % mod;
  while (y > 0) {
    if (y & 1)
      res = (1ll * res * x) % mod;
    y = y >> 1;
    x = (1ll * x * x) % mod;
  }
  return res;
}
ll ncr(ll n, ll r) {
  ll res = 1;
  if (r > n - r)
    r = n - r;
  for (ll i = 0; i < r; i++) {
    res *= n - i;
    res /= i + 1;
  }
  return res;
}
ll max(ll a, ll b) { return (a > b) ? a : b; }
bool prime(ll n) {
  ll i;
  for (i = 2; i <= sqrt(n); i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}
bool sortbysec(const pair<ll, ll> &a, const pair<ll, ll> &b) {
  if (a.second == b.second)
    return a.first < b.first;
  return (a.second < b.second);
}
// https://www.youtube.com/watch?v=WTJSt4wP2ME

ll rr[] = {
    0, 1, 1, 1, 0, -1, -1, -1,
};
ll cc[] = {1, 1, 0, -1, -1, -1, 0, 1};

ll a[MAXN], ans[MAXN];

signed main() {
  bolt;
#ifndef ONLINE_JUDGE
  freopen("input00.txt", "r", stdin);
  freopen("output00.txt", "w", stdout);
#endif
  ll x;
  cin >> x;
  ll ans = 0;
  ans += 1000 * (x / 500);
  x %= 500;
  ans += (5 * (x / 5));
  cout << ans;
}