Problem p01769 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

#define foreach(it, c)                                                         \
  for (__typeof__((c).begin()) it = (c).begin(); it != (c).end(); ++it)
template <typename T> void print_container(ostream &os, const T &c) {
  const char *_s = " ";
  if (!c.empty()) {
    __typeof__(c.begin()) last = --c.end();
    foreach (it, c) {
      os << *it;
      if (it != last)
        os << _s;
    }
  }
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const deque<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}

template <typename T> void print(T a, int n, const string &split = " ") {
  for (int i = 0; i < n; i++) {
    cout << a[i];
    if (i + 1 != n)
      cout << split;
  }
  cout << endl;
}
template <typename T>
void print2d(T a, int w, int h, int width = -1, int br = 0) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (width != -1)
        cout.width(width);
      cout << a[i][j] << ' ';
    }
    cout << endl;
  }
  while (br--)
    cout << endl;
}
template <typename T> void input(T &a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}
#define dump(v) (cerr << #v << ": " << v << endl)

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define clr(a, x) memset(a, x, sizeof(a))
#define sz(a) ((int)(a).size())
#define mp(a, b) make_pair(a, b)
#define ten(n) ((long long)(1e##n))

template <typename T, typename U> void upmin(T &a, const U &b) {
  a = min<T>(a, b);
}
template <typename T, typename U> void upmax(T &a, const U &b) {
  a = max<T>(a, b);
}
template <typename T> void uniq(T &a) {
  sort(a.begin(), a.end());
  a.erase(unique(a.begin(), a.end()), a.end());
}
template <class T> string to_s(const T &a) {
  ostringstream os;
  os << a;
  return os.str();
}
template <class T> T to_T(const string &s) {
  istringstream is(s);
  T res;
  is >> res;
  return res;
}
void fast_io() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
bool in_rect(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}

typedef long long ll;
typedef pair<int, int> pint;

const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

int main() {
  int n, l;
  cin >> n >> l;

  vector<int> x(n), a(n);
  input(x, n);
  input(a, n);

  const int mod = ten(9) + 7;
  static int dp[5555][5555];
  dp[n][l] = 1;
  for (int i = n - 1; i >= 0; --i) {
    int ways = 0;
    for (int p = l; p >= x[i]; --p) {
      if ((p - x[i]) % a[i] == 0)
        dp[i][p] = ways;

      (ways += dp[i + 1][p]) %= mod;
    }
  }

  int res = 0;
  rep(p, l)(res += dp[0][p]) %= mod;
  cout << res << endl;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

#define foreach(it, c)                                                         \
  for (__typeof__((c).begin()) it = (c).begin(); it != (c).end(); ++it)
template <typename T> void print_container(ostream &os, const T &c) {
  const char *_s = " ";
  if (!c.empty()) {
    __typeof__(c.begin()) last = --c.end();
    foreach (it, c) {
      os << *it;
      if (it != last)
        os << _s;
    }
  }
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const deque<T> &c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &c) {
  print_container(os, c);
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}

template <typename T> void print(T a, int n, const string &split = " ") {
  for (int i = 0; i < n; i++) {
    cout << a[i];
    if (i + 1 != n)
      cout << split;
  }
  cout << endl;
}
template <typename T>
void print2d(T a, int w, int h, int width = -1, int br = 0) {
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (width != -1)
        cout.width(width);
      cout << a[i][j] << ' ';
    }
    cout << endl;
  }
  while (br--)
    cout << endl;
}
template <typename T> void input(T &a, int n) {
  for (int i = 0; i < n; ++i)
    cin >> a[i];
}
#define dump(v) (cerr << #v << ": " << v << endl)

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define clr(a, x) memset(a, x, sizeof(a))
#define sz(a) ((int)(a).size())
#define mp(a, b) make_pair(a, b)
#define ten(n) ((long long)(1e##n))

template <typename T, typename U> void upmin(T &a, const U &b) {
  a = min<T>(a, b);
}
template <typename T, typename U> void upmax(T &a, const U &b) {
  a = max<T>(a, b);
}
template <typename T> void uniq(T &a) {
  sort(a.begin(), a.end());
  a.erase(unique(a.begin(), a.end()), a.end());
}
template <class T> string to_s(const T &a) {
  ostringstream os;
  os << a;
  return os.str();
}
template <class T> T to_T(const string &s) {
  istringstream is(s);
  T res;
  is >> res;
  return res;
}
void fast_io() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
bool in_rect(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}

typedef long long ll;
typedef pair<int, int> pint;

const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};

int main() {
  int n, l;
  cin >> n >> l;

  vector<int> x(n), a(n);
  input(x, n);
  input(a, n);

  const int mod = ten(9) + 7;
  static int dp[5555][5555];
  dp[n][l] = 1;
  for (int i = n - 1; i >= 0; --i) {
    int ways = 0;
    for (int p = l; p >= x[i]; --p) {
      if (a[i] == 0 && p == x[i] || a[i] != 0 && (p - x[i]) % a[i] == 0)
        dp[i][p] = ways;

      (ways += dp[i + 1][p]) %= mod;
    }
  }

  int res = 0;
  rep(p, l)(res += dp[0][p]) %= mod;
  cout << res << endl;
}