Problem p03013 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define eee(a) (cerr << (#a) << ": " << (a) << endl);

using ll = long long;
using pint = pair<int, int>;
using pll = pair<ll, ll>;
using mint = map<int, int>;

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

const char sp = ' ';
const char cmm = ',';
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LINF = 1e18;

ll mod(ll a, ll b) { return (a % b + b) % b; }
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void Judge(bool b) { b ? Yes() : No(); }
void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
void JUDGE(bool b) { b ? YES() : NO(); }
ll powMod(ll b, ll e, ll m) {
  ll r = 1;
  while (e > 0) {
    if (e & 1)
      r = (r % m) * (b % m) % m;
    b = (b % m) * (b % m) % m;
    e >>= 1;
  }
  return r;
}
double distance(ll x1, ll y1, ll x2, ll y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T> void ppp(T n) { cout << n << endl; }
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  s << '[';
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << ", ";
  }
  s << ']';
  return s;
}

struct aaa {
  aaa() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  };
} fastio;

vector<ll> dp(110000, 0);
int main() {

  int n, m;
  cin >> n >> m;

  vector<int> a(m);
  rep(i, m) cin >> a[i];

  int idx = 0;
  dp[0] = 1;
  dp[1] = 1;
  if (m != 0 and a[0] == 1) {
    dp[1] = 0;
    ++idx;
  }

  for (int i = 2; i <= n; ++i) {
    if (i == a[idx]) {
      ++idx;
      continue;
    }
    dp[i] = dp[i - 2] + dp[i - 1];
    dp[i] %= MOD;
  }
  ppp(dp[n]);

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define eee(a) (cerr << (#a) << ": " << (a) << endl);

using ll = long long;
using pint = pair<int, int>;
using pll = pair<ll, ll>;
using mint = map<int, int>;

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

const char sp = ' ';
const char cmm = ',';
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LINF = 1e18;

ll mod(ll a, ll b) { return (a % b + b) % b; }
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a * b / gcd(a, b); }
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void Judge(bool b) { b ? Yes() : No(); }
void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
void JUDGE(bool b) { b ? YES() : NO(); }
ll powMod(ll b, ll e, ll m) {
  ll r = 1;
  while (e > 0) {
    if (e & 1)
      r = (r % m) * (b % m) % m;
    b = (b % m) * (b % m) % m;
    e >>= 1;
  }
  return r;
}
double distance(ll x1, ll y1, ll x2, ll y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T> void ppp(T n) { cout << n << endl; }
template <typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}
template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  int len = v.size();
  s << '[';
  for (int i = 0; i < len; ++i) {
    s << v[i];
    if (i < len - 1)
      s << ", ";
  }
  s << ']';
  return s;
}

struct aaa {
  aaa() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  };
} fastio;

vector<ll> dp(110000, 0);
int main() {

  int n, m;
  cin >> n >> m;

  vector<int> a(m);
  rep(i, m) cin >> a[i];

  int idx = 0;
  dp[0] = 1;
  dp[1] = 1;
  if (m != 0 and a[0] == 1) {
    dp[1] = 0;
    ++idx;
  }

  for (int i = 2; i <= n; ++i) {
    if (idx < m and i == a[idx]) {
      ++idx;
      continue;
    }
    dp[i] = dp[i - 2] + dp[i - 1];
    dp[i] %= MOD;
  }
  ppp(dp[n]);

  return 0;
}