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

#include <algorithm>
#include <bits/stdc++.h>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <iomanip>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
// setbase - cout << setbase (16); cout << 100 << endl; Prints 64
// setfill -   cout << setfill ('x') << setw (5); cout << 77 << endl; prints
// xxx77 setprecision - cout << setprecision (14) << f << endl; Prints x.xxxx
// cout.precision(x)  cout<<fixed<<val;  // prints x digits after decimal in val
using namespace std;
using namespace __gnu_pbds;

#define sp << " " <<
#define mod 1000000007
#define PI 3.14159265358979323
#define y second
#define x first
#define pb push_back
#define mp make_pair
#define sz(a) a.size()
#define pqueue priority_queue<ll>
// #define pdqueue priority_queue< ll,vector<ll> ,greater< ll > >
#define codejamDebug(x) cout << "Case #" << x << ": ";
#define debug(x) cout << #x << " :" << x << endl;
#define rep(i, n) for (long long i = 0; i < n; i++)
#define f(i, a, b) for (long long i = a; i < b; i++)
#define fd(i, a, b) for (long long i = a; i >= b; i--)
#define sync                                                                   \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long int ll;
typedef long double ld;
typedef unsigned long long int ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<string> vs;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

// Handle:cyber_rajat

int main(int argc, char const *argv[]) {
  sync;
  // #ifndef ONLINE_JUDGE
  // freopen("input.txt","r",stdin);
  // freopen("output.txt","w",stdout);
  // #endif
  ll n;
  cin >> n;
  ll q = n / 500;
  ll rem = n % 500;
  ll q1 = rem / 5;
  ll rem1 = rem % 5;
  cout << q * 1000 + q1 * 5 << endl;
  return 0;
}


Error: WA

Fixed submission:

#include <algorithm>
#include <bits/stdc++.h>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <iomanip>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
// setbase - cout << setbase (16); cout << 100 << endl; Prints 64
// setfill -   cout << setfill ('x') << setw (5); cout << 77 << endl; prints
// xxx77 setprecision - cout << setprecision (14) << f << endl; Prints x.xxxx
// cout.precision(x)  cout<<fixed<<val;  // prints x digits after decimal in val
using namespace std;
using namespace __gnu_pbds;

#define sp << " " <<
#define mod 1000000007
#define PI 3.14159265358979323
#define y second
#define x first
#define pb push_back
#define mp make_pair
#define sz(a) a.size()
#define pqueue priority_queue<ll>
// #define pdqueue priority_queue< ll,vector<ll> ,greater< ll > >
#define codejamDebug(x) cout << "Case #" << x << ": ";
#define debug(x) cout << #x << " :" << x << endl;
#define rep(i, n) for (long long i = 0; i < n; i++)
#define f(i, a, b) for (long long i = a; i < b; i++)
#define fd(i, a, b) for (long long i = a; i >= b; i--)
#define sync                                                                   \\
  ios_base::sync_with_stdio(false);                                            \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long int ll;
typedef long double ld;
typedef unsigned long long int ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<string> vs;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

// Handle:cyber_rajat

int main(int argc, char const *argv[]) {
  sync;
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  ll n;
  cin >> n;
  ll q = n / 500;
  ll rem = n % 500;
  ll q1 = rem / 5;
  ll rem1 = rem % 5;
  cout << q * 1000 + q1 * 5 << endl;
  return 0;
}