Language: C++

#include <bits/stdc++.h>  // include all standard C++ libraries

using namespace std;

// Loops
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=int(a);i<int(b);++i)
#define _rrep(i,n) rrepi(i,n,0)
#define rrepi(i,a,b) for(int i=int(a)-1;i>=int(b);--i)

#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(xi, x) for (auto&& xi : x)
// Note: we can use rep(i,N) or rep(i,from,to)


// typedef
using ll = long long;
template <class T> using vec = vector<T>;
using vi   = vector<int>;
using vvi  = vector<vi>;
using vvvi = vector<vvi>;
using pii  = pair<int, int>;


// Constants

// Shorter repr for frequently used terms
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second


// Algorithms
#define all(x) (x).begin(), (x).end()
#define uniq(v) v.erase( unique(all(v)), v.end() )
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))

template<class T> pair<T, size_t> max(vector<T> &x){ auto it = max_element(all(x)); return mp(*it, it-x.begin()); }
template<class T> pair<T, size_t> min(vector<T> &x){ auto it = min_element(all(x)); return mp(*it, it-x.begin()); }

template<class T> inline bool chmax(T &maxval, const T &newval) { if (maxval<newval) { maxval=newval; return 1; } return 0; }
template<class T> inline bool chmin(T &minval, const T &newval) { if (minval>newval) { minval=newval; return 1; } return 0; }

// Utilities
// Grid world utilities
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
#define inside(H,W,y,x) 0<=(x) && (x)<(W) && 0<=(y) && (y)<(H)

inline int in() {int x; cin >> x; return x;} // read int from cin
inline  ll IN() {ll x; cin >> x; return x;}  // read ll from cin



// Debug
#ifdef LOCAL
  #include "dump.hpp"
  #define debug(x) cerr << #x << ": " << x << '\n'
#else
  #define dump(...)
  #define debug(x)
#endif

// Paste snippets here!!

// 

int main(){
  cin.tie(0); ios::sync_with_stdio(false);    // Magic for faster cin
  unsigned ll n; cin >> n;
  vector<unsigned ll> a(n);
  rep(i,n) { cin >> a[i]; if(a[i]==0) { cout << 0 << endl; return 0; }
  unsigned ll ret = 1;
  rep(i,n){
    unsigned ll ret_old = ret;
    ret *= a[i];
    if(ret/a[i]!=ret_old) {cout << -1 << endl; return 0;}
  }
  if(ret>1000000000000000000) cout << -1 << endl;
  else cout << ret << endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:74:15: error: expected initializer before 'n'
   74 |   unsigned ll n; cin >> n;
      |               ^
a.cc:74:25: error: 'n' was not declared in this scope; did you mean 'yn'?
   74 |   unsigned ll n; cin >> n;
      |                         ^
      |                         yn
a.cc:77:15: error: expected initializer before 'ret'
   77 |   unsigned ll ret = 1;
      |               ^~~
a.cc:79:17: error: expected initializer before 'ret_old'
   79 |     unsigned ll ret_old = ret;
      |                 ^~~~~~~
a.cc:80:5: error: 'ret' was not declared in this scope; did you mean 'rep'?
   80 |     ret *= a[i];
      |     ^~~
      |     rep
a.cc:81:18: error: 'ret_old' was not declared in this scope
   81 |     if(ret/a[i]!=ret_old) {cout << -1 << endl; return 0;}
      |                  ^~~~~~~
a.cc:83:6: error: 'ret' was not declared in this scope; did you mean 'rep'?
   83 |   if(ret>1000000000000000000) cout << -1 << endl;
      |      ^~~
      |      rep
a.cc:86:2: error: expected '}' at end of input
   86 | }
      |  ^
a.cc:72:11: note: to match this '{'
   72 | int main(){
      |           ^