Problem p03465 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define rep(i, a, b) for (long long(i) = (a); i < (b); i++)
#define all(i) i.begin(), i.end()
#define debug(i) std::cerr << "debug " << #i << " " << i << std::endl

template <typename T1, typename T2>
std::ostream &operator<<(std::ostream &os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream &operator<<(std::ostream &os, std::vector<T> vec) {
  for (int i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return a > b && (a = b, true);
}

long long pow_mod(long long a, long long b, long long mod = -1) {
  if ((a == 0) || (mod != -1 && a % mod == 0)) {
    return 0;
  }

  long long x = 1;

  while (b > 0) {
    if (b & 1) {
      x = (mod != -1) ? (x * a) % mod : x * a;
    }
    a = (mod != -1) ? (a * a) % mod : a * a;
    b >>= 1;
  }
  return x;
}

// const long long MOD = 998244353;
const long long MOD = 1e9 + 7;

using ll = long long;
using P = std::pair<ll, ll>;

int main() {
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);

  ll n;
  std::cin >> n;

  std::bitset<400010> make;

  make[0] = true;

  ll sum = 0;

  rep(i, 0, n) {
    ll a;
    std::cin >> a;
    sum += a;

    make |= (make << a);
  }

  rep(i, (sum + 1) / 2, sum + 1) {
    if (make[i]) {
      std::cout << i << "\n";
      return 0;
    }
  }

  return 0;
}

Fixed submission:
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define rep(i, a, b) for (long long(i) = (a); i < (b); i++)
#define all(i) i.begin(), i.end()
#define debug(i) std::cerr << "debug " << #i << " " << i << std::endl

template <typename T1, typename T2>
std::ostream &operator<<(std::ostream &os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream &operator<<(std::ostream &os, std::vector<T> vec) {
  for (int i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  return a > b && (a = b, true);
}

long long pow_mod(long long a, long long b, long long mod = -1) {
  if ((a == 0) || (mod != -1 && a % mod == 0)) {
    return 0;
  }

  long long x = 1;

  while (b > 0) {
    if (b & 1) {
      x = (mod != -1) ? (x * a) % mod : x * a;
    }
    a = (mod != -1) ? (a * a) % mod : a * a;
    b >>= 1;
  }
  return x;
}

// const long long MOD = 998244353;
const long long MOD = 1e9 + 7;

using ll = long long;
using P = std::pair<ll, ll>;

int main() {
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);

  ll n;
  std::cin >> n;

  std::bitset<4000100> make;

  make[0] = true;

  ll sum = 0;

  rep(i, 0, n) {
    ll a;
    std::cin >> a;
    sum += a;

    make |= (make << a);
  }

  rep(i, (sum + 1) / 2, sum + 1) {
    if (make[i]) {
      std::cout << i << "\n";
      return 0;
    }
  }

  return 0;
}