Problem p03651 (C++)

Buggy submission (status: Runtime Error):
#pragma GCC optimize("O3")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
#define IINF 10e8
#define INF 1 << 30
#define MOD 1000000007
#define mod 10007
#define REP(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define REPE(i, a, n) for (ll i = a; i <= (ll)(n); i++)
#define Endl endl
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define chmax(x, y) x = mmax(x, y)
#define chmin(x, y) x = mmin(x, y)
#define all(x) (x).begin(), (x).end()
#define siz(x) (ll)(x).size()
#define PI acos(-1.0)
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> Pin;
typedef pair<ll, ll> Pll;
template <class T> using V = vector<T>;
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
long long LCM(long long a, long long b) { return a / GCD(a, b) * b; }
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, -1, 0, 1};
int ddx[8] = {-1, 0, 1, 0, 1, 1, -1, -1};
int ddy[8] = {0, -1, 0, 1, 1, -1, 1, -1};
ll cmp(pair<ll, ll> a, pair<ll, ll> b) {
  if (a.se != b.se)
    return a.se < b.se;
  else
    return a.fi < b.fi;
}
//----------------------------------------------------------------------

//----------------------------------------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  //-------------------------------
  ll n, k;
  cin >> n >> k;
  V<ll> a(n);
  bool abc = 0;
  for (ll i = 0; i < n; i++) {
    cin >> a[i];
    if (a[i] == k)
      abc = 1;
  }
  if (abc == 1) {
    cout << "POSSIBLE" << endl;
    return 0;
  }
  sort(all(a));
  if (a[n - 1] < k) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  ll minc = INF;
  for (ll i = 0; i < n - 1; i++) {
    chmin(minc, a[i + 1] - a[i]);
  }
  if (minc == 1) {
    cout << "POSSIBLE" << endl;
    return 0;
  } else {
    for (ll i = 0; i < n; i++) {
      if (a[i] > k) {
        if ((a[i] - k) % minc == 0) {
          cout << "POSSIBLE" << endl;
          return 0;
        }
      }
    }
  }
  cout << "IMPOSSIBLE" << endl;
  //-------------------------------
  return 0;
}
//----------------------------------------------------------------------


Fixed submission:
#pragma GCC optimize("O3")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
#define IINF 10e8
#define INF 1 << 30
#define MOD 1000000007
#define mod 10007
#define REP(i, a, n) for (ll i = a; i < (ll)(n); i++)
#define REPE(i, a, n) for (ll i = a; i <= (ll)(n); i++)
#define Endl endl
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define chmax(x, y) x = mmax(x, y)
#define chmin(x, y) x = mmin(x, y)
#define all(x) (x).begin(), (x).end()
#define siz(x) (ll)(x).size()
#define PI acos(-1.0)
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> Pin;
typedef pair<ll, ll> Pll;
template <class T> using V = vector<T>;
long long GCD(long long a, long long b) { return b ? GCD(b, a % b) : a; }
long long LCM(long long a, long long b) { return a / GCD(a, b) * b; }
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, -1, 0, 1};
int ddx[8] = {-1, 0, 1, 0, 1, 1, -1, -1};
int ddy[8] = {0, -1, 0, 1, 1, -1, 1, -1};
ll cmp(pair<ll, ll> a, pair<ll, ll> b) {
  if (a.se != b.se)
    return a.se < b.se;
  else
    return a.fi < b.fi;
}
//----------------------------------------------------------------------

//----------------------------------------------------------------------
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  //-------------------------------
  ll n, k;
  cin >> n >> k;
  V<ll> a(n);
  bool abc = 0;
  for (ll i = 0; i < n; i++) {
    cin >> a[i];
    if (a[i] == k)
      abc = 1;
  }
  if (abc == 1) {
    cout << "POSSIBLE" << endl;
    return 0;
  }
  sort(all(a));
  if (a[n - 1] < k) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  ll minc = INF;
  for (ll i = 1; i < n; i++) {
    if (a[i] == a[i - 1])
      continue;
    chmin(minc, a[i] - a[i - 1]);
  }
  if (minc == 1) {
    cout << "POSSIBLE" << endl;
    return 0;
  } else {
    for (ll i = 0; i < n; i++) {
      if (a[i] > k) {
        if ((a[i] - k) % minc == 0) {
          cout << "POSSIBLE" << endl;
          return 0;
        }
      }
    }
  }
  cout << "IMPOSSIBLE" << endl;
  //-------------------------------
  return 0;
}
//----------------------------------------------------------------------