Problem p02658 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iostream>
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define forn(i, n) for (int i = 0; i < (int)(n); ++i)
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)
#define ford(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define fore(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)

using namespace __gnu_pbds;
using namespace std;

typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    ordered_set;

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef long long i64;
typedef vector<i64> vi64;
typedef vector<vi64> vvi64;
typedef pair<i64, i64> pi64;
typedef double ld;
typedef unsigned long long ui64;

template <class T> bool uin(T &a, T b) { return a > b ? (a = b, true) : false; }
template <class T> bool uax(T &a, T b) { return a < b ? (a = b, true) : false; }
const int mod = 1000000007;
i64 poww(i64 a, i64 b) {
  a %= mod;
  i64 res = 1;
  while (b) {
    if (b & 1)
      res = res * a % mod;

    a = a * a % mod;
    b /= 2;
  }
  return res;
}
i64 inv(i64 a) { return poww(a, mod - 2); }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // ifstream fin(".in");
  // ofstream fout(".in");
  i64 n, x;
  cin >> n;
  i64 pr = 1;
  bool is1 = false, is2 = false;
  i64 mx = 1e18;
  forn(i, n) {
    cin >> x;

    // cout<<x<<" "<<(mx/pr)<<"\n";
    if (x == 0) {
      is2 = true;
      pr = 0;
    }
    if (pr > mx || x > (mx / pr) || is1) {
      is1 = true;

    } else
      pr *= x;
  }
  // cout<<is1<<" "<<is2<<" ";
  if (is1 && !is2)
    cout << "-1";
  else
    cout << pr;

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iostream>
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define forn(i, n) for (int i = 0; i < (int)(n); ++i)
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)
#define ford(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define fore(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)

using namespace __gnu_pbds;
using namespace std;

typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    ordered_set;

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef long long i64;
typedef vector<i64> vi64;
typedef vector<vi64> vvi64;
typedef pair<i64, i64> pi64;
typedef double ld;
typedef unsigned long long ui64;

template <class T> bool uin(T &a, T b) { return a > b ? (a = b, true) : false; }
template <class T> bool uax(T &a, T b) { return a < b ? (a = b, true) : false; }
const int mod = 1000000007;
i64 poww(i64 a, i64 b) {
  a %= mod;
  i64 res = 1;
  while (b) {
    if (b & 1)
      res = res * a % mod;

    a = a * a % mod;
    b /= 2;
  }
  return res;
}
i64 inv(i64 a) { return poww(a, mod - 2); }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  // ifstream fin(".in");
  // ofstream fout(".in");
  i64 n, x;
  cin >> n;
  i64 pr = 1;
  bool is1 = false, is2 = false;
  i64 mx = 1e18;
  forn(i, n) {
    cin >> x;

    // cout<<x<<" "<<(mx/pr)<<"\n";
    if (x == 0) {
      is2 = true;
      pr = 0;
      break;
    }
    if (pr > mx || x > (mx / pr) || is1) {
      is1 = true;

    } else
      pr *= x;
  }
  // cout<<is1<<" "<<is2<<" ";
  if (is1 && !is2)
    cout << "-1";
  else
    cout << pr;

  return 0;
}