Problem p03008 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define FOR(i, n, m) for (int i = n; i < (int)m; i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define pb push_back
using namespace std;
using ll = std::int_fast64_t;
using P = pair<ll, ll>;
constexpr ll inf = 1000000000;
constexpr ll mod = 1000000007;
constexpr long double eps = 1e-15;
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  os << to_string(p.first) << " " << to_string(p.second);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  REP(i, v.size()) {
    if (i)
      os << " ";
    os << to_string(v[i]);
  }
  return os;
}

// number//
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

struct modint {
  ll n;

public:
  modint(const ll n = 0) : n((n % mod + mod) % mod) {}
  static modint pow(modint a, ll m) {
    // static vector<modint> v(1000010, -1);
    // if(m == mod - 2 && v[a.n] != -1) return v[a.n];
    // int tmp = a.n;
    modint r = 1;
    while (m > 0) {
      if (m & 1) {
        r *= a;
      }
      a = (a * a);
      m /= 2;
    }
    // if(m == mod - 2) return v[tmp] = r;
    return r;
  }
  modint &operator++() {
    *this += 1;
    return *this;
  }
  modint &operator--() {
    *this -= 1;
    return *this;
  }
  modint operator++(int) {
    modint ret = *this;
    *this += 1;
    return ret;
  }
  modint operator--(int) {
    modint ret = *this;
    *this -= 1;
    return ret;
  }
  modint operator~() const { return (this->pow(n, mod - 2)); } // inverse
  friend bool operator==(const modint &lhs, const modint &rhs) {
    return lhs.n == rhs.n;
  }
  friend bool operator<(const modint &lhs, const modint &rhs) {
    return lhs.n < rhs.n;
  }
  friend bool operator>(const modint &lhs, const modint &rhs) {
    return lhs.n > rhs.n;
  }
  friend modint &operator+=(modint &lhs, const modint &rhs) {
    lhs.n += rhs.n;
    if (lhs.n >= mod)
      lhs.n -= mod;
    return lhs;
  }
  friend modint &operator-=(modint &lhs, const modint &rhs) {
    lhs.n -= rhs.n;
    if (lhs.n < 0)
      lhs.n += mod;
    return lhs;
  }
  friend modint &operator*=(modint &lhs, const modint &rhs) {
    lhs.n = (lhs.n * rhs.n) % mod;
    return lhs;
  }
  friend modint &operator/=(modint &lhs, const modint &rhs) {
    lhs.n = (lhs.n * (~rhs).n) % mod;
    return lhs;
  }
  friend modint operator+(const modint &lhs, const modint &rhs) {
    return modint(lhs.n + rhs.n);
  }
  friend modint operator-(const modint &lhs, const modint &rhs) {
    return modint(lhs.n - rhs.n);
  }
  friend modint operator*(const modint &lhs, const modint &rhs) {
    return modint(lhs.n * rhs.n);
  }
  friend modint operator/(const modint &lhs, const modint &rhs) {
    return modint(lhs.n * (~rhs).n);
  }
};
istream &operator>>(istream &is, modint m) {
  is >> m.n;
  return is;
}
ostream &operator<<(ostream &os, modint m) {
  os << m.n;
  return os;
}

struct binomial_coefficient {
private:
  int m;
  vector<modint> fact;

public:
  binomial_coefficient(int m) : m(m) {
    fact.resize(m);
    fact[0] = 1;
    for (int i = 1; i < m; i++)
      fact[i] = fact[i - 1] * i;
  }
  modint combination(int n, int k) {
    if (n < 0 || k < 0 || n < k)
      return 0;
    return fact[n] / fact[n - k] / fact[k];
  }
};

// graph //
using weight = long long;
struct edge {
  int to;
  weight w;
};
template <typename T> struct vedge : edge {
  T v;
};
struct graph {
private:
  int n;
  bool weighted;
  bool tree;
  vector<vector<edge>> g;

public:
  graph(int n, bool tree = false)
      : n(n), weighted(false), tree(tree), g(vector<vector<edge>>(n)) {}
  vector<edge> &operator[](int i) { return g[i]; }
  int size() { return n; }
  bool isweighted() { return weighted; }
  bool istree() { return tree; }
  void add_edge(int s, int t, weight w = 1) {
    g[s].push_back({t, w});
    g[t].push_back({s, w});
    if (w != 1)
      weighted = true;
  }
  void add_dedge(int s, int t, weight w = 1) {
    g[s].push_back({t, w});
    if (w != 1)
      weighted = true;
  }
};
template <typename T> struct vgraph {
public:
private:
  int n;
  bool weighted;
  bool tree;
  vector<vector<vedge<T>>> g;
  vgraph(int n, bool tree = false)
      : n(n), weighted(false), tree(tree), g(vector<vector<vedge<T>>>(n)) {}
  vector<edge> &operator[](int i) { return g[i]; }
  int size() { return n; }
  bool isweighted() { return weighted; }
  bool istree() { return tree; }
  void add_edge(int s, int t, T v, weight w = 1) {
    g[s].push_back({t, w, v});
    g[t].push_back({s, w, v});
    if (w != 1)
      weighted = true;
  }
  void add_dedge(int s, int t, T v, weight w = 1) {
    g[s].push_back({t, w, v});
    if (w != 1)
      weighted = true;
  }
  graph build_graph() {
    graph ret(n);
    for (auto v : g)
      for (auto e : g[v]) {
        ret.add_dedge(v, e.to, e.w);
      }
    return ret;
  }
};

vector<weight> shortest_path(graph &g, int s) {
  int n = g.size();
  vector<weight> path(n, -1);
  if (g.isweighted() && !g.istree()) { // dijkstra
    priority_queue<pair<weight, int>, vector<pair<weight, int>>,
                   greater<pair<weight, int>>>
        q;
    path[s] = 0;
    q.push({0, s});
    while (!q.empty()) {
      weight cost = q.top().first;
      int p = q.top().second;
      q.pop();
      if (path[p] != cost)
        continue;
      for (auto e : g[p]) {
        if (path[e.to] == -1 || path[e.to] > cost + e.w) {
          path[e.to] = cost + e.w;
          q.push({path[e.to], e.to});
        }
      }
    }
  } else { // bfs
    queue<int> q;
    path[s] = 0;
    q.push(s);
    while (!q.empty()) {
      int p = q.front();
      q.pop();
      for (auto e : g[p]) {
        if (path[e.to] == -1) {
          path[e.to] = path[p] + 1;
          q.push(e.to);
        }
      }
    }
  }
  return path;
}

using mi = modint;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n;
  ll ga, sa, ba, gb, sb, bb;
  cin >> n;
  cin >> ga >> sa >> ba >> gb >> sb >> bb;
  ll dong2 = n;
  ll ans = n;
  REP(i, n + 1) REP(j, n + 1) {
    if (i * ga + j * sa > n)
      continue;
    ll k = 0;
    if (ba < bb)
      k = ((n - i * ga - j * sa) / ba);
    dong2 = max(dong2, n + i * (gb - ga) + j * (sb - sa) + k * (bb - ba));
  }
  REP(i, dong2 + 1) REP(j, dong2 + 1) {
    if (i * gb + j * sb > dong2)
      continue;
    ll k = 0;
    if (bb < ba)
      k = ((dong2 - i * gb - j * sb) / bb);
    ans = max(ans, dong2 + i * (ga - gb) + j * (sa - sb) + k * (ba - bb));
  }
  cout << ans << endl;
  return 0;
}

// ---------------------------------------


Fixed submission:
#include <bits/stdc++.h>
#define FOR(i, n, m) for (int i = n; i < (int)m; i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define pb push_back
using namespace std;
using ll = std::int_fast64_t;
using P = pair<ll, ll>;
constexpr ll inf = 1000000000;
constexpr ll mod = 1000000007;
constexpr long double eps = 1e-15;
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  os << to_string(p.first) << " " << to_string(p.second);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  REP(i, v.size()) {
    if (i)
      os << " ";
    os << to_string(v[i]);
  }
  return os;
}

// number//
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

struct modint {
  ll n;

public:
  modint(const ll n = 0) : n((n % mod + mod) % mod) {}
  static modint pow(modint a, ll m) {
    // static vector<modint> v(1000010, -1);
    // if(m == mod - 2 && v[a.n] != -1) return v[a.n];
    // int tmp = a.n;
    modint r = 1;
    while (m > 0) {
      if (m & 1) {
        r *= a;
      }
      a = (a * a);
      m /= 2;
    }
    // if(m == mod - 2) return v[tmp] = r;
    return r;
  }
  modint &operator++() {
    *this += 1;
    return *this;
  }
  modint &operator--() {
    *this -= 1;
    return *this;
  }
  modint operator++(int) {
    modint ret = *this;
    *this += 1;
    return ret;
  }
  modint operator--(int) {
    modint ret = *this;
    *this -= 1;
    return ret;
  }
  modint operator~() const { return (this->pow(n, mod - 2)); } // inverse
  friend bool operator==(const modint &lhs, const modint &rhs) {
    return lhs.n == rhs.n;
  }
  friend bool operator<(const modint &lhs, const modint &rhs) {
    return lhs.n < rhs.n;
  }
  friend bool operator>(const modint &lhs, const modint &rhs) {
    return lhs.n > rhs.n;
  }
  friend modint &operator+=(modint &lhs, const modint &rhs) {
    lhs.n += rhs.n;
    if (lhs.n >= mod)
      lhs.n -= mod;
    return lhs;
  }
  friend modint &operator-=(modint &lhs, const modint &rhs) {
    lhs.n -= rhs.n;
    if (lhs.n < 0)
      lhs.n += mod;
    return lhs;
  }
  friend modint &operator*=(modint &lhs, const modint &rhs) {
    lhs.n = (lhs.n * rhs.n) % mod;
    return lhs;
  }
  friend modint &operator/=(modint &lhs, const modint &rhs) {
    lhs.n = (lhs.n * (~rhs).n) % mod;
    return lhs;
  }
  friend modint operator+(const modint &lhs, const modint &rhs) {
    return modint(lhs.n + rhs.n);
  }
  friend modint operator-(const modint &lhs, const modint &rhs) {
    return modint(lhs.n - rhs.n);
  }
  friend modint operator*(const modint &lhs, const modint &rhs) {
    return modint(lhs.n * rhs.n);
  }
  friend modint operator/(const modint &lhs, const modint &rhs) {
    return modint(lhs.n * (~rhs).n);
  }
};
istream &operator>>(istream &is, modint m) {
  is >> m.n;
  return is;
}
ostream &operator<<(ostream &os, modint m) {
  os << m.n;
  return os;
}

struct binomial_coefficient {
private:
  int m;
  vector<modint> fact;

public:
  binomial_coefficient(int m) : m(m) {
    fact.resize(m);
    fact[0] = 1;
    for (int i = 1; i < m; i++)
      fact[i] = fact[i - 1] * i;
  }
  modint combination(int n, int k) {
    if (n < 0 || k < 0 || n < k)
      return 0;
    return fact[n] / fact[n - k] / fact[k];
  }
};

// graph //
using weight = long long;
struct edge {
  int to;
  weight w;
};
template <typename T> struct vedge : edge {
  T v;
};
struct graph {
private:
  int n;
  bool weighted;
  bool tree;
  vector<vector<edge>> g;

public:
  graph(int n, bool tree = false)
      : n(n), weighted(false), tree(tree), g(vector<vector<edge>>(n)) {}
  vector<edge> &operator[](int i) { return g[i]; }
  int size() { return n; }
  bool isweighted() { return weighted; }
  bool istree() { return tree; }
  void add_edge(int s, int t, weight w = 1) {
    g[s].push_back({t, w});
    g[t].push_back({s, w});
    if (w != 1)
      weighted = true;
  }
  void add_dedge(int s, int t, weight w = 1) {
    g[s].push_back({t, w});
    if (w != 1)
      weighted = true;
  }
};
template <typename T> struct vgraph {
public:
private:
  int n;
  bool weighted;
  bool tree;
  vector<vector<vedge<T>>> g;
  vgraph(int n, bool tree = false)
      : n(n), weighted(false), tree(tree), g(vector<vector<vedge<T>>>(n)) {}
  vector<edge> &operator[](int i) { return g[i]; }
  int size() { return n; }
  bool isweighted() { return weighted; }
  bool istree() { return tree; }
  void add_edge(int s, int t, T v, weight w = 1) {
    g[s].push_back({t, w, v});
    g[t].push_back({s, w, v});
    if (w != 1)
      weighted = true;
  }
  void add_dedge(int s, int t, T v, weight w = 1) {
    g[s].push_back({t, w, v});
    if (w != 1)
      weighted = true;
  }
  graph build_graph() {
    graph ret(n);
    for (auto v : g)
      for (auto e : g[v]) {
        ret.add_dedge(v, e.to, e.w);
      }
    return ret;
  }
};

vector<weight> shortest_path(graph &g, int s) {
  int n = g.size();
  vector<weight> path(n, -1);
  if (g.isweighted() && !g.istree()) { // dijkstra
    priority_queue<pair<weight, int>, vector<pair<weight, int>>,
                   greater<pair<weight, int>>>
        q;
    path[s] = 0;
    q.push({0, s});
    while (!q.empty()) {
      weight cost = q.top().first;
      int p = q.top().second;
      q.pop();
      if (path[p] != cost)
        continue;
      for (auto e : g[p]) {
        if (path[e.to] == -1 || path[e.to] > cost + e.w) {
          path[e.to] = cost + e.w;
          q.push({path[e.to], e.to});
        }
      }
    }
  } else { // bfs
    queue<int> q;
    path[s] = 0;
    q.push(s);
    while (!q.empty()) {
      int p = q.front();
      q.pop();
      for (auto e : g[p]) {
        if (path[e.to] == -1) {
          path[e.to] = path[p] + 1;
          q.push(e.to);
        }
      }
    }
  }
  return path;
}

using mi = modint;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n;
  ll ga, sa, ba, gb, sb, bb;
  cin >> n;
  cin >> ga >> sa >> ba >> gb >> sb >> bb;
  ll dong2 = n;
  ll ans = n;
  REP(i, n + 1) REP(j, n + 1) {
    if (i * ga + j * sa > n)
      continue;
    ll k = 0;
    if (ba < bb)
      k = ((n - i * ga - j * sa) / ba);
    dong2 = max(dong2, n + i * (gb - ga) + j * (sb - sa) + k * (bb - ba));
  }
  ans = dong2;
  if (ga > gb && sa > sb && ba > bb) {
    REP(i, dong2 + 1) REP(j, dong2 + 1) {
      if (i * gb + j * sb > dong2)
        continue;
      ll k = 0;
      if (bb < ba)
        k = ((dong2 - i * gb - j * sb) / bb);
      ans = max(ans, dong2 + i * (ga - gb) + j * (sa - sb) + k * (ba - bb));
    }
  } else if (ga > gb && sa > sb) {
    REP(i, dong2 + 1) {
      if (i * gb > dong2)
        continue;
      ll j = ((dong2 - i * gb) / sb);
      ans = max(ans, dong2 + i * (ga - gb) + j * (sa - sb));
    }
  } else if (sa > sb && ba > bb) {
    REP(i, dong2 + 1) {
      if (i * sb > dong2)
        continue;
      ll j = ((dong2 - i * sb) / bb);
      ans = max(ans, dong2 + i * (sa - sb) + j * (ba - bb));
    }
  } else if (ba > bb && ga > gb) {
    REP(i, dong2 + 1) {
      if (i * bb > dong2)
        continue;
      ll j = ((dong2 - i * bb) / gb);
      ans = max(ans, dong2 + i * (ba - bb) + j * (ga - gb));
    }
  } else if (ga > gb) {
    ll i = (dong2 / gb);
    ans = max(ans, dong2 + i * (ga - gb));
  } else if (sa > sb) {
    ll i = (dong2 / sb);
    ans = max(ans, dong2 + i * (sa - sb));
  } else if (ba > bb) {
    ll i = (dong2 / bb);
    ans = max(ans, dong2 + i * (ba - bb));
  }
  cout << ans << endl;
  return 0;
}

// ---------------------------------------