Problem p02970 (C++)

Buggy submission (status: Runtime Error):
//----------BHAVIK DIWANI(PICT_COMP)---------------
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define test                                                                   \
  ll t;                                                                        \
  cin >> t;                                                                    \
  while (t--)
#define fastio                                                                 \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define mod 1000000007
#define ll long long
#define int long long
#define ull unsigned long long
#define MAX 1000005
#define pb push_back
#define mkp make_pair
#define vi vector<int>
#define pii pair<int, int>
#define endl '\n'
#define vs vector<string>
#define mii map<int, int>
#define msi map<string, int>
#define vpii vector<pair<int, int>>
#define vpsi vector<pair<string, int>>
#define forci(p, q) for (int i = p; i < q; i++)
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); }
ull power(ull a, ull b) {
  a %= mod;
  ull res = 1;
  while (b > 0) {
    if (b & 1)
      res = res * a % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return res % mod;
}
ll modmul(ll x, ll y) { return (x * y) % mod; }
ll modadd(ll x, ll y) { return (x + y) % mod; }
ll modsub(ll x, ll y) { return (x - y + mod) % mod; }
ll fact[1000007] = {0};
void facto() {
  fact[0] = 1;
  fact[1] = 1;
  for (int i = 2; i < 1000007; i++)
    fact[i] = (fact[i - 1] * i) % mod;
}
ll ncr(ll n, ll r) {
  ll res = 1;
  res = fact[n];
  res = (res * (power(fact[r], mod - 2))) % mod;
  res = (res * (power(fact[n - r], mod - 2))) % mod;
  return res;
}
ll npr(ll n, ll r) {
  ll res = 1;
  res = fact[n];
  res = (res * (power(fact[n - r], mod - 2))) % mod;
  return res;
}
inline long long toint(const std::string &s) {
  std::stringstream ss;
  ss << s;
  long long x;
  ss >> x;
  return x;
}
inline std::string tostring(long long number) {
  std::stringstream ss;
  ss << number;
  return ss.str();
}
inline std::string tobin(long long x) { return std::bitset<63>(x).to_string(); }
/*bool prime[MAX];
ull sieve(){memset(prime,true,sizeof(prime));for(ull
p=2;p*p<MAX;p++){if(prime[p]==true){for(ull
i=2*p;i<MAX;i+=p){prime[i]=false;}}}prime[0]=0;prime[1]=0;
}*/
/*int inv[1000001]={0};
void findinverse(){inv[1] = 1;for(int i = 2; i <=1e6 ; ++i)	inv[i] = (mod -
(mod/i) * inv[mod%i] % mod) % mod;}
*/
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    orderedSet;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    orderedMultiset;
int solve() {
  int n, d;
  cin >> n >> d;
  cout << (n + 2 * d) / (2 * d + 1) << endl;
}
signed main() {
  fastio;
  //	test
  solve();
}


Fixed submission:
//----------BHAVIK DIWANI(PICT_COMP)---------------
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define test                                                                   \
  ll t;                                                                        \
  cin >> t;                                                                    \
  while (t--)
#define fastio                                                                 \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define mod 1000000007
#define ll long long
#define int long long
#define ull unsigned long long
#define MAX 1000005
#define pb push_back
#define mkp make_pair
#define vi vector<int>
#define pii pair<int, int>
#define endl '\n'
#define vs vector<string>
#define mii map<int, int>
#define msi map<string, int>
#define vpii vector<pair<int, int>>
#define vpsi vector<pair<string, int>>
#define forci(p, q) for (int i = p; i < q; i++)
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); }
ull power(ull a, ull b) {
  a %= mod;
  ull res = 1;
  while (b > 0) {
    if (b & 1)
      res = res * a % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return res % mod;
}
ll modmul(ll x, ll y) { return (x * y) % mod; }
ll modadd(ll x, ll y) { return (x + y) % mod; }
ll modsub(ll x, ll y) { return (x - y + mod) % mod; }
ll fact[1000007] = {0};
void facto() {
  fact[0] = 1;
  fact[1] = 1;
  for (int i = 2; i < 1000007; i++)
    fact[i] = (fact[i - 1] * i) % mod;
}
ll ncr(ll n, ll r) {
  ll res = 1;
  res = fact[n];
  res = (res * (power(fact[r], mod - 2))) % mod;
  res = (res * (power(fact[n - r], mod - 2))) % mod;
  return res;
}
ll npr(ll n, ll r) {
  ll res = 1;
  res = fact[n];
  res = (res * (power(fact[n - r], mod - 2))) % mod;
  return res;
}
inline long long toint(const std::string &s) {
  std::stringstream ss;
  ss << s;
  long long x;
  ss >> x;
  return x;
}
inline std::string tostring(long long number) {
  std::stringstream ss;
  ss << number;
  return ss.str();
}
inline std::string tobin(long long x) { return std::bitset<63>(x).to_string(); }
/*bool prime[MAX];
ull sieve(){memset(prime,true,sizeof(prime));for(ull
p=2;p*p<MAX;p++){if(prime[p]==true){for(ull
i=2*p;i<MAX;i+=p){prime[i]=false;}}}prime[0]=0;prime[1]=0;
}*/
/*int inv[1000001]={0};
void findinverse(){inv[1] = 1;for(int i = 2; i <=1e6 ; ++i)	inv[i] = (mod -
(mod/i) * inv[mod%i] % mod) % mod;}
*/
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    orderedSet;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    orderedMultiset;
int solve() {
  int n, d;
  cin >> n >> d;
  cout << (n + 2 * d) / (2 * d + 1) << endl;
  return 0;
}
signed main() {
  fastio;
  //	test
  solve();
}