Problem p02653 (C++) — buggy submission, verdict: Time Limit Exceeded

/*

                                             `-:://:::-
                                           `//:-------:/:`
                                          .+:--.......--:+`
                                         `+:--..`````..--//`
                                         .o:--..`` ``..--:o`
                                         .o:--...```..---+/`
                                       `/y+o/---....---:+o.
                                   `...````-os+/:---:/+o/--.`
              `-/+++++/:.      `...`       :h+d+oooo+/+-`   ...
            `/++//:::://++-`....`         -.`//````````:`     `..`
           `o+/::------://o/`           `-` -.          -`       `..`
 `---.-o/:./o/::-..``..-ЗАПУСКАЕМ      ..  ..            -`        `... ``..``
  `....o+:-++/:--.```..-://s.        `-`  .-              -`          `-o:
 .-//::::/:-`
          `:s+/:--....-::/+s-`      .-   `-                -` -///:--------:/:`
           ./s+//:::::://oo-``..НЕЙРОННУЮ: СЕТЬ:::::::-`РАБОТЯГИ
 `+:--........--:/`
            .:ooo+++++osso-`    `.:-...`/` ./::-------:/:`   -`
 :+--..``````.--:+:...-+:-`
             `.-/+++++/+-.-`    -.   ``:so:/:--.......--:+`
 `-```````o+/+--..`````..--:o/-..:s+:.
                 ```````:``.. `-`     -`
 `+:--..`````..--/+-.../.`````..-o:--.......---/o.    `
                        `:  `:-      -.  .o:--..`` ``..--:o`   `-`
 `:o+:--------:+o-`
                         `-`-...    ..   .o/--...```..--:+/`    `-`
 `oy/so/////++o/.`
                          -/`  `-` `- ``+s/o/:---...---:++.      `-`
 .-../d://///:-.`
                `.---..``-..-    .-/..`````-oo+/:::::/+o+-        `-``-`  `-.
 ````
             `:++++/+++++-  ..``.-/:`      /y-:/++o++/:.`..`       ./.   `-
            -++/::::::://+/..:-``:` ..   `-.`  ```.```    `..`   `..`-` `-
       ``  -o//:--....-::/++` -.-`   `-`.-`                 `..`..`  `-.-
  -----ss+:++/:--.```..-://s.  /.     `::                    `-:.     ./`
  `````/:..+o/::-..``.--:/+s. ..-`   `-``-`                 ..` `-`  `-`-`
          `-s+/::-----::/+oo---``-` ..    .:-    ```      .-`     .-.-  `-`
           `:oo+//::://+os/..:`..-/:`      :y.-:::::::.`.-`        ./-`  `-`
            `./+oooooooo+/.`-    .-:...`.. .//:-------://`        `- `..` `:.
              ``.-::::-.``-/`  `-` `-  `oo:+:--.......--:/`      `-
 `.:--h.``..```
                          -.-`.-    .-   `+:--..`````..--//`    `-
 /s-//::::::::.
                         -` `/-      ..  .o:--..`` ``..--:o.```.-
 `//:--------://`
                        -` .-`.-`
 -.`-o/--...```..--:+/.``-:....``:-.+:--....`...--:+`
                       ..`-.   `-.   ``:os:o/:---...---:++.  `-
 ``///+:-..``````.--:+-````-.`
              `.:///////.-`      .:-..` -``-+o+/:::::/+o/.  `-
 `:+:-..`````..--:o/:--/ys+-
            `-++///////+o/. ``....`-.    :` `.:++++++/:.`  .- -o/---......---/o.
 `.`
           `++//:-----::/+o:..`     .-`   :    ```````    .- `+so+:--------:++-`
  `````:-``:o/::-..`..--:/+o`         -.  `-             .- `../../+o+////+o+:.`
  -----syo/o+/:--.```..-://s.          .-` `-           .-        `...
 ``-:////:-``
       .` `/s//:--....-::/+s.            -. `-`        .-       `..`
           .+o+/:::--:://+s/-..`          .::+y  ```  .-     `..`
            ./oo++////+oso-`   `....       :y-+:::::::/`   ...
             `.:+oooooo/-`         `....-. .//:-------:/:-.`
                ``...``                 /+:+:--.......--:+`
                                         `+:--..`````..--//`
                                         .o:--..`` ``..--:o`
                                         .+/--...```..--:+/`
                                         `-o/:---...---:++.
                                          `-+o+/:---:/+o/.
                                            `.:+oooo+/-.`
                                               ``````
*/

#ifdef aimbot
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,avx,avx2")
#include <immintrin.h>
#endif

#define hur(f, g)                                                              \\
  template <class c> int f(c a) {                                              \\
    if (sizeof(c) == 8)                                                        \\
      return g##ll(a);                                                         \\
    else                                                                       \\
      return g(a);                                                             \\
  }
hur(popc, __builtin_popcount) hur(ctz, __builtin_ctz) hur(clz, __builtin_clz)

/*
        - place bitset modifications here
*/

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <istream>
#include <limits>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <string>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define random escape__from__random__aetuhoetnuhshe
#define mt make_tuple
#define x first
#define y second
#define pb push_back
#define mp make_pair
#define le(v) ((int)v.size())
#define f(i, n) for (int i = 0; i < (n); i++)
#define rof(i, n) for (int i = ((n)-1); i >= 0; i--)
#define apply(v, act)                                                          \\
  for (auto &x : v) {                                                          \\
    act;                                                                       \\
  }
#define log(args...)                                                           \\
  {                                                                            \\
    string s = #args;                                                          \\
    deque<string> deq;                                                         \\
    string buf = "";                                                           \\
    int bal = 0;                                                               \\
    for (char c : s) {                                                         \\
      if (c == '(' || c == '[' || c == '{') {                                  \\
        bal++;                                                                 \\
      } else if (c == ')' || c == ']' || c == '}') {                           \\
        bal--;                                                                 \\
      } else {                                                                 \\
        if (bal == 0) {                                                        \\
          if (c == ',') {                                                      \\
            deq.pb(buf);                                                       \\
            buf = "";                                                          \\
          } else {                                                             \\
            if (c != ' ') {                                                    \\
              buf += c;                                                        \\
            }                                                                  \\
          }                                                                    \\
        }                                                                      \\
      }                                                                        \\
    }                                                                          \\
    if (!buf.empty()) {                                                        \\
      deq.pb(buf);                                                             \\
    }                                                                          \\
    smart_io::precall_print();                                                 \\
    smart_io::_print(deq, args);                                               \\
  }

    inline int min(const int &x, const int &y) {
  return (((y - x) >> (32 - 1)) & (x ^ y)) ^ x;
}
inline int max(const int &x, const int &y) {
  return (((y - x) >> (32 - 1)) & (x ^ y)) ^ y;
}
inline long long min(const long long &x, const long long &y) {
  return (((y - x) >> (64 - 1)) & (x ^ y)) ^ x;
}
inline long long max(const long long &x, const long long &y) {
  return (((y - x) >> (64 - 1)) & (x ^ y)) ^ y;
}

#define print                                                                  \\
  smart_io::precall_print();                                                   \\
  cout,

#define scan cin,

#ifdef fast_allocator
const int MAXMEM = 200 * 1000 * 1024;
char _memory[MAXMEM];
size_t _ptr = 0;
void *operator new(size_t _x) {
  _ptr += _x;
  assert(_ptr < MAXMEM);
  return _memory + _ptr - _x;
}
void operator delete(void *) noexcept {}
#endif

using namespace std;

char string_in_buffer[(int)260];

void fast_scan(int &x) { scanf("%d", &x); }
void fast_scan(long long &x) { scanf("%lld", &x); }
void fast_scan(unsigned long long &x) { scanf("%llu", &x); }
void fast_scan(double &x) { scanf("%lf", &x); }
void fast_scan(long double &x) { scanf("%Lf", &x); }
void fast_scan(char &x) {
  scanf("%c", &x);
  if (x == '\\n') {
    fast_scan(x);
  }
}
void fast_scan(string &x) {
  scanf("%s", string_in_buffer);
  x = string(string_in_buffer);
}

template <class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
  fast_scan(p.first);
  fast_scan(p.second);
}

template <class T> void fast_scan(vector<T> &v) {
  for (auto &x : v)
    fast_scan(x);
}

void fast_print(const int &x) { printf("%d", x); }
void fast_print(const unsigned int &x) { printf("%u", x); }
void fast_print(const long long &x) { printf("%lld", x); }
void fast_print(const unsigned long long &x) { printf("%llu", x); }
void fast_print(const char &x) { printf("%c", x); };
// void fast_print(__int128 x) {
// 	if (x == 0) { fast_print('0'); return; }
// 	if (x < 0) {
// 		fast_print('-');
// 		x = -x;
// 	}
// 	__int128 p = 1;
// 	while (x / (p * 10)) p *= 10;
// 	while (p) {
// 		__int128 symb = x / p;
// 		fast_print((int)symb);
// 		x -= p * symb;
// 		p /= 10;
// 	}
// };
void fast_print(const double &x) { printf("%.15lf", x); }
void fast_print(const long double &x) { printf("%.15Lf", x); }
void fast_print(const string &x) { printf("%s", x.c_str()); }
void fast_print(const char v[]) { fast_print((string)v); }

template <class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
  fast_print(p.first);
  fast_print(' ');
  fast_print(p.second);
}

template <class T> void fast_print(const vector<T> &v) {
  if (v.empty())
    return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print(' ');
    fast_print(v[i]);
  }
}

template <class T> void fast_print(const vector<vector<T>> &v) {
  if (v.empty())
    return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print('\\n');
    fast_print(v[i]);
  }
}

template <class T> void fast_print(const T &v) {
  for (const auto &x : v) {
    fast_print(x);
    fast_print(' ');
  }
}

using namespace std;

namespace smart_io {
string print_start = "";
string sep = " ";
bool first_print = false;

void precall_print() {
  fast_print(print_start);
  print_start = "\\n";
  first_print = true;
}

void _print(deque<string>) {}
template <class T, class... Args>
void _print(deque<string> names, T elem, Args... args) {
  if (!first_print) {
    fast_print("\\n");
  } else {
    first_print = false;
  }
  fast_print(names.front());
  fast_print(" = ");
  fast_print(elem);
  names.pop_front();
  _print(names, args...);
}
} // namespace smart_io

template <class T> ostream &operator,(ostream &os, const T &object) {
  if (!smart_io::first_print) {
    fast_print(smart_io::sep);
  } else {
    smart_io::first_print = false;
  }
  fast_print(object);
  return os;
}

template <class T> istream &operator,(istream &is, T &object) {
  fast_scan(object);
  return is;
}

namespace random {
using namespace std::chrono;
mt19937 rng(duration_cast<milliseconds>(system_clock::now().time_since_epoch())
                .count());
uniform_real_distribution<> prob_dist(0.0, 1.0);
}; // namespace random

namespace typedefs {
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef long double ld;
} // namespace typedefs

namespace numbers_operation {
template <class T> inline T floor_mod(T a, const T &b) {
  a %= b;
  if (a < 0)
    a += b;
  return a;
}
} // namespace numbers_operation

using namespace numbers_operation;
using namespace typedefs;
using namespace random;

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
template <ll MOD> struct Ring {
  ll value = 0;
  Ring() {}
  Ring(int _value) {
    value = _value;
    value = floor_mod(value, MOD);
  }
  Ring(ll _value) {
    value = _value;
    value = floor_mod(value, MOD);
  }
  Ring pow(ll p) const {
    Ring r = 1;
    Ring x;
    x.value = value;
    while (p) {
      if (p & 1)
        r *= x;
      x *= x;
      p /= 2;
    }
    return r;
  }
  Ring inv() const { return pow(MOD - 2); }
  void operator*=(const Ring<MOD> &b) {
    value *= b.value;
    value = floor_mod(value, MOD);
  }
  friend Ring operator*(Ring<MOD> a, const Ring<MOD> &b) {
    a *= b;
    return a;
  }
  void operator+=(const Ring<MOD> &b) {
    value += b.value;
    value -= (value >= MOD) * MOD;
  }
  friend Ring operator+(Ring a, const Ring &b) {
    a += b;
    return a;
  }
  void operator-=(const Ring<MOD> &b) {
    value -= b.value;
    value += (value < 0) ? MOD : 0;
  }
  friend Ring operator-(Ring a, const Ring &b) {
    a -= b;
    return a;
  }
  void operator/=(const Ring<MOD> &b) { (*this) *= b.inv(); }
  friend Ring operator/(Ring a, const Ring &b) {
    a /= b;
    return a;
  }
  bool operator==(const Ring<MOD> &b) { return value == b.value; }
  bool operator!=(const Ring<MOD> &b) { return value != b.value; }
  friend void fast_print(const Ring<MOD> &b) { fast_print(b.value); }
};

typedef Ring<MOD> num;

int n, a, b;

vector<string> moves(string s, int a, int b) {
  vector<string> rez;
  // for (int i = 0; i <= le(s) - a; i++) {
  for (int j = 0; j <= le(s) - b; j++) {
    string t = s;
    // for (int k = 0; k < a; k++) {
    // 	t[i + k] = '0';
    // }
    for (int k = 0; k < b; k++) {
      t[j + k] = '1';
    }
    rez.pb(t);
  }
  // }
  for (int i = 0; i <= le(s) - a; i++) {
    // for (int j = 0; j <= le(s) - b; j++) {
    string t = s;
    // for (int k = 0; k < b; k++) {
    // 	t[j + k] = '1';
    // }
    for (int k = 0; k < a; k++) {
      t[i + k] = '0';
    }
    rez.pb(t);
    // }
  }
  return rez;
}

int bfs(int n, int a, int b) {
  deque<string> deq{string(n, '0')};
  set<string> used;
  while (!deq.empty()) {
    string s = deq[0];
    deq.pop_front();
    if (used.count(s))
      continue;
    used.insert(s);
    for (string t : moves(s, a, b)) {
      deq.pb(t);
    }
  }
  // for (string s : used) {
  // 	if (s.back() == '1' && s[le(s) - 2] == '0') {
  // 		print s;
  // 	}
  // }
  // print used;
  return le(used);
}

int mem[2][5010][5010];
int smem[5010][5010];
num dp(int, int, bool);
num dpsum(int n, int l) {
  if (n < 0)
    return 0;
  if (smem[n][l] != -1)
    return smem[n][l];
  smem[n][l] = (dp(n, l, false) + dpsum(n - 1, l + 1)).value;
  return smem[n][l];
}
int md[5010];
num dpref(int n) {
  if (n < 0)
    return 0;
  if (md[n] != -1)
    return md[n];
  md[n] = (dp(n, 0, false) + dpref(n - 1)).value;
  return md[n];
}
num dp(int n, int l, bool can_one) {
  if (n < 0)
    return 0;
  if (n == 0)
    return l >= a;
  if (mem[can_one][n][l] != -1)
    return mem[can_one][n][l];
  num rez = 0;
  if (l >= a) {
    rez = num(2).pow(n + can_one - 1);
  } else {
    if (can_one) {
      rez += dpref(n - 1) - dpref(n - b);
      rez += dpsum(n - b, l + b);
    }
    rez += dp(n - 1, l + 1, true);
  }
  mem[can_one][n][l] = rez.value;
  return rez;
}

signed main(signed argc, char *argv[]) {
  memset(mem, -1, sizeof mem);
  memset(smem, -1, sizeof smem);
  memset(md, -1, sizeof md);
  scan n, a, b;
  if (a < b)
    swap(a, b);
  print dp(n, 0, true);
}


Error: TLE

Fixed submission:

/*

                                             `-:://:::-
                                           `//:-------:/:`
                                          .+:--.......--:+`
                                         `+:--..`````..--//`
                                         .o:--..`` ``..--:o`
                                         .o:--...```..---+/`
                                       `/y+o/---....---:+o.
                                   `...````-os+/:---:/+o/--.`
              `-/+++++/:.      `...`       :h+d+oooo+/+-`   ...
            `/++//:::://++-`....`         -.`//````````:`     `..`
           `o+/::------://o/`           `-` -.          -`       `..`
 `---.-o/:./o/::-..``..-ЗАПУСКАЕМ      ..  ..            -`        `... ``..``
  `....o+:-++/:--.```..-://s.        `-`  .-              -`          `-o:
 .-//::::/:-`
          `:s+/:--....-::/+s-`      .-   `-                -` -///:--------:/:`
           ./s+//:::::://oo-``..НЕЙРОННУЮ: СЕТЬ:::::::-`РАБОТЯГИ
 `+:--........--:/`
            .:ooo+++++osso-`    `.:-...`/` ./::-------:/:`   -`
 :+--..``````.--:+:...-+:-`
             `.-/+++++/+-.-`    -.   ``:so:/:--.......--:+`
 `-```````o+/+--..`````..--:o/-..:s+:.
                 ```````:``.. `-`     -`
 `+:--..`````..--/+-.../.`````..-o:--.......---/o.    `
                        `:  `:-      -.  .o:--..`` ``..--:o`   `-`
 `:o+:--------:+o-`
                         `-`-...    ..   .o/--...```..--:+/`    `-`
 `oy/so/////++o/.`
                          -/`  `-` `- ``+s/o/:---...---:++.      `-`
 .-../d://///:-.`
                `.---..``-..-    .-/..`````-oo+/:::::/+o+-        `-``-`  `-.
 ````
             `:++++/+++++-  ..``.-/:`      /y-:/++o++/:.`..`       ./.   `-
            -++/::::::://+/..:-``:` ..   `-.`  ```.```    `..`   `..`-` `-
       ``  -o//:--....-::/++` -.-`   `-`.-`                 `..`..`  `-.-
  -----ss+:++/:--.```..-://s.  /.     `::                    `-:.     ./`
  `````/:..+o/::-..``.--:/+s. ..-`   `-``-`                 ..` `-`  `-`-`
          `-s+/::-----::/+oo---``-` ..    .:-    ```      .-`     .-.-  `-`
           `:oo+//::://+os/..:`..-/:`      :y.-:::::::.`.-`        ./-`  `-`
            `./+oooooooo+/.`-    .-:...`.. .//:-------://`        `- `..` `:.
              ``.-::::-.``-/`  `-` `-  `oo:+:--.......--:/`      `-
 `.:--h.``..```
                          -.-`.-    .-   `+:--..`````..--//`    `-
 /s-//::::::::.
                         -` `/-      ..  .o:--..`` ``..--:o.```.-
 `//:--------://`
                        -` .-`.-`
 -.`-o/--...```..--:+/.``-:....``:-.+:--....`...--:+`
                       ..`-.   `-.   ``:os:o/:---...---:++.  `-
 ``///+:-..``````.--:+-````-.`
              `.:///////.-`      .:-..` -``-+o+/:::::/+o/.  `-
 `:+:-..`````..--:o/:--/ys+-
            `-++///////+o/. ``....`-.    :` `.:++++++/:.`  .- -o/---......---/o.
 `.`
           `++//:-----::/+o:..`     .-`   :    ```````    .- `+so+:--------:++-`
  `````:-``:o/::-..`..--:/+o`         -.  `-             .- `../../+o+////+o+:.`
  -----syo/o+/:--.```..-://s.          .-` `-           .-        `...
 ``-:////:-``
       .` `/s//:--....-::/+s.            -. `-`        .-       `..`
           .+o+/:::--:://+s/-..`          .::+y  ```  .-     `..`
            ./oo++////+oso-`   `....       :y-+:::::::/`   ...
             `.:+oooooo/-`         `....-. .//:-------:/:-.`
                ``...``                 /+:+:--.......--:+`
                                         `+:--..`````..--//`
                                         .o:--..`` ``..--:o`
                                         .+/--...```..--:+/`
                                         `-o/:---...---:++.
                                          `-+o+/:---:/+o/.
                                            `.:+oooo+/-.`
                                               ``````
*/

#ifdef aimbot
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,avx,avx2")
#include <immintrin.h>
#endif

#define hur(f, g)                                                              \\
  template <class c> int f(c a) {                                              \\
    if (sizeof(c) == 8)                                                        \\
      return g##ll(a);                                                         \\
    else                                                                       \\
      return g(a);                                                             \\
  }
hur(popc, __builtin_popcount) hur(ctz, __builtin_ctz) hur(clz, __builtin_clz)

/*
        - place bitset modifications here
*/

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <istream>
#include <limits>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <string>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define random escape__from__random__aetuhoetnuhshe
#define mt make_tuple
#define x first
#define y second
#define pb push_back
#define mp make_pair
#define le(v) ((int)v.size())
#define f(i, n) for (int i = 0; i < (n); i++)
#define rof(i, n) for (int i = ((n)-1); i >= 0; i--)
#define apply(v, act)                                                          \\
  for (auto &x : v) {                                                          \\
    act;                                                                       \\
  }
#define log(args...)                                                           \\
  {                                                                            \\
    string s = #args;                                                          \\
    deque<string> deq;                                                         \\
    string buf = "";                                                           \\
    int bal = 0;                                                               \\
    for (char c : s) {                                                         \\
      if (c == '(' || c == '[' || c == '{') {                                  \\
        bal++;                                                                 \\
      } else if (c == ')' || c == ']' || c == '}') {                           \\
        bal--;                                                                 \\
      } else {                                                                 \\
        if (bal == 0) {                                                        \\
          if (c == ',') {                                                      \\
            deq.pb(buf);                                                       \\
            buf = "";                                                          \\
          } else {                                                             \\
            if (c != ' ') {                                                    \\
              buf += c;                                                        \\
            }                                                                  \\
          }                                                                    \\
        }                                                                      \\
      }                                                                        \\
    }                                                                          \\
    if (!buf.empty()) {                                                        \\
      deq.pb(buf);                                                             \\
    }                                                                          \\
    smart_io::precall_print();                                                 \\
    smart_io::_print(deq, args);                                               \\
  }

    inline int min(const int &x, const int &y) {
  return (((y - x) >> (32 - 1)) & (x ^ y)) ^ x;
}
inline int max(const int &x, const int &y) {
  return (((y - x) >> (32 - 1)) & (x ^ y)) ^ y;
}
inline long long min(const long long &x, const long long &y) {
  return (((y - x) >> (64 - 1)) & (x ^ y)) ^ x;
}
inline long long max(const long long &x, const long long &y) {
  return (((y - x) >> (64 - 1)) & (x ^ y)) ^ y;
}

#define print                                                                  \\
  smart_io::precall_print();                                                   \\
  cout,

#define scan cin,

#ifdef fast_allocator
const int MAXMEM = 200 * 1000 * 1024;
char _memory[MAXMEM];
size_t _ptr = 0;
void *operator new(size_t _x) {
  _ptr += _x;
  assert(_ptr < MAXMEM);
  return _memory + _ptr - _x;
}
void operator delete(void *) noexcept {}
#endif

using namespace std;

char string_in_buffer[(int)260];

void fast_scan(int &x) { scanf("%d", &x); }
void fast_scan(long long &x) { scanf("%lld", &x); }
void fast_scan(unsigned long long &x) { scanf("%llu", &x); }
void fast_scan(double &x) { scanf("%lf", &x); }
void fast_scan(long double &x) { scanf("%Lf", &x); }
void fast_scan(char &x) {
  scanf("%c", &x);
  if (x == '\\n') {
    fast_scan(x);
  }
}
void fast_scan(string &x) {
  scanf("%s", string_in_buffer);
  x = string(string_in_buffer);
}

template <class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
  fast_scan(p.first);
  fast_scan(p.second);
}

template <class T> void fast_scan(vector<T> &v) {
  for (auto &x : v)
    fast_scan(x);
}

void fast_print(const int &x) { printf("%d", x); }
void fast_print(const unsigned int &x) { printf("%u", x); }
void fast_print(const long long &x) { printf("%lld", x); }
void fast_print(const unsigned long long &x) { printf("%llu", x); }
void fast_print(const char &x) { printf("%c", x); };
// void fast_print(__int128 x) {
// 	if (x == 0) { fast_print('0'); return; }
// 	if (x < 0) {
// 		fast_print('-');
// 		x = -x;
// 	}
// 	__int128 p = 1;
// 	while (x / (p * 10)) p *= 10;
// 	while (p) {
// 		__int128 symb = x / p;
// 		fast_print((int)symb);
// 		x -= p * symb;
// 		p /= 10;
// 	}
// };
void fast_print(const double &x) { printf("%.15lf", x); }
void fast_print(const long double &x) { printf("%.15Lf", x); }
void fast_print(const string &x) { printf("%s", x.c_str()); }
void fast_print(const char v[]) { fast_print((string)v); }

template <class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
  fast_print(p.first);
  fast_print(' ');
  fast_print(p.second);
}

template <class T> void fast_print(const vector<T> &v) {
  if (v.empty())
    return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print(' ');
    fast_print(v[i]);
  }
}

template <class T> void fast_print(const vector<vector<T>> &v) {
  if (v.empty())
    return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print('\\n');
    fast_print(v[i]);
  }
}

template <class T> void fast_print(const T &v) {
  for (const auto &x : v) {
    fast_print(x);
    fast_print(' ');
  }
}

using namespace std;

namespace smart_io {
string print_start = "";
string sep = " ";
bool first_print = false;

void precall_print() {
  fast_print(print_start);
  print_start = "\\n";
  first_print = true;
}

void _print(deque<string>) {}
template <class T, class... Args>
void _print(deque<string> names, T elem, Args... args) {
  if (!first_print) {
    fast_print("\\n");
  } else {
    first_print = false;
  }
  fast_print(names.front());
  fast_print(" = ");
  fast_print(elem);
  names.pop_front();
  _print(names, args...);
}
} // namespace smart_io

template <class T> ostream &operator,(ostream &os, const T &object) {
  if (!smart_io::first_print) {
    fast_print(smart_io::sep);
  } else {
    smart_io::first_print = false;
  }
  fast_print(object);
  return os;
}

template <class T> istream &operator,(istream &is, T &object) {
  fast_scan(object);
  return is;
}

namespace random {
using namespace std::chrono;
mt19937 rng(duration_cast<milliseconds>(system_clock::now().time_since_epoch())
                .count());
uniform_real_distribution<> prob_dist(0.0, 1.0);
}; // namespace random

namespace typedefs {
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef long double ld;
} // namespace typedefs

namespace numbers_operation {
template <class T> inline T floor_mod(T a, const T &b) {
  a %= b;
  if (a < 0)
    a += b;
  return a;
}
} // namespace numbers_operation

using namespace numbers_operation;
using namespace typedefs;
using namespace random;

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
template <ll MOD> struct Ring {
  ll value = 0;
  Ring() {}
  Ring(int _value) {
    value = _value;
    value = floor_mod(value, MOD);
  }
  Ring(ll _value) {
    value = _value;
    value = floor_mod(value, MOD);
  }
  Ring pow(ll p) const {
    Ring r = 1;
    Ring x;
    x.value = value;
    while (p) {
      if (p & 1)
        r *= x;
      x *= x;
      p /= 2;
    }
    return r;
  }
  Ring inv() const { return pow(MOD - 2); }
  void operator*=(const Ring<MOD> &b) {
    value *= b.value;
    value = floor_mod(value, MOD);
  }
  friend Ring operator*(Ring<MOD> a, const Ring<MOD> &b) {
    a *= b;
    return a;
  }
  void operator+=(const Ring<MOD> &b) {
    value += b.value;
    value -= (value >= MOD) * MOD;
  }
  friend Ring operator+(Ring a, const Ring &b) {
    a += b;
    return a;
  }
  void operator-=(const Ring<MOD> &b) {
    value -= b.value;
    value += (value < 0) ? MOD : 0;
  }
  friend Ring operator-(Ring a, const Ring &b) {
    a -= b;
    return a;
  }
  void operator/=(const Ring<MOD> &b) { (*this) *= b.inv(); }
  friend Ring operator/(Ring a, const Ring &b) {
    a /= b;
    return a;
  }
  bool operator==(const Ring<MOD> &b) { return value == b.value; }
  bool operator!=(const Ring<MOD> &b) { return value != b.value; }
  friend void fast_print(const Ring<MOD> &b) { fast_print(b.value); }
};

typedef Ring<MOD> num;

int n, a, b;

vector<string> moves(string s, int a, int b) {
  vector<string> rez;
  // for (int i = 0; i <= le(s) - a; i++) {
  for (int j = 0; j <= le(s) - b; j++) {
    string t = s;
    // for (int k = 0; k < a; k++) {
    // 	t[i + k] = '0';
    // }
    for (int k = 0; k < b; k++) {
      t[j + k] = '1';
    }
    rez.pb(t);
  }
  // }
  for (int i = 0; i <= le(s) - a; i++) {
    // for (int j = 0; j <= le(s) - b; j++) {
    string t = s;
    // for (int k = 0; k < b; k++) {
    // 	t[j + k] = '1';
    // }
    for (int k = 0; k < a; k++) {
      t[i + k] = '0';
    }
    rez.pb(t);
    // }
  }
  return rez;
}

int bfs(int n, int a, int b) {
  deque<string> deq{string(n, '0')};
  set<string> used;
  while (!deq.empty()) {
    string s = deq[0];
    deq.pop_front();
    if (used.count(s))
      continue;
    used.insert(s);
    for (string t : moves(s, a, b)) {
      deq.pb(t);
    }
  }
  // for (string s : used) {
  // 	if (s.back() == '1' && s[le(s) - 2] == '0') {
  // 		print s;
  // 	}
  // }
  // print used;
  return le(used);
}

int mem[2][5010][5010];
int smem[5010][5010];
num dp(int, int, bool);
num dpsum(int n, int l) {
  if (n < 0)
    return 0;
  if (smem[n][l] != -1)
    return smem[n][l];
  smem[n][l] = (dp(n, l, false) + dpsum(n - 1, l + 1)).value;
  return smem[n][l];
}
num dp(int n, int l, bool can_one) {
  if (n < 0)
    return 0;
  if (n == 0)
    return l >= a;
  if (mem[can_one][n][l] != -1)
    return mem[can_one][n][l];
  num rez = 0;
  if (l >= a) {
    rez = num(2).pow(n + can_one - 1);
  } else {
    if (can_one) {
      for (int ones = 1; ones < b; ones++) {
        rez += dp(n - ones, 0, false);
      }
      rez += dpsum(n - b, l + b);
    }
    rez += dp(n - 1, l + 1, true);
  }
  mem[can_one][n][l] = rez.value;
  return rez;
}

signed main(signed argc, char *argv[]) {
  memset(mem, -1, sizeof mem);
  memset(smem, -1, sizeof smem);
  scan n, a, b;
  if (a < b)
    swap(a, b);
  print dp(n, 0, true);
}