#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; //#define int long long typedef long long ll; typedef unsigned long long ul; typedef unsigned int ui; const ll mod = 1000000007; const ll INF = (1e+18) + 7; typedef pairP; #define stop char nyaa;cin>>nyaa; #define rep(i,n) for(int i=0;i=0;i--) #define Rep(i,sta,n) for(int i=sta;i=1;i--) #define Rep1(i,sta,n) for(int i=sta;i<=n;i++) #define all(v) (v).begin(),(v).end() typedef pair LP; typedef long double ld; typedef pair LDP; const ld eps = 1e-6; const ld pi = acos(-1.0); //typedef vector> mat; typedef vector vec; void debug(vector &v) { rep(i, v.size()) { if (i > 0)cout << " "; cout << v[i]; } cout << endl; } ll mod_pow(ll a, ll n) { ll res = 1; while (n) { if (n & 1)res = res * a%mod; a = a * a%mod; n >>= 1; } return res; } struct modint { ll n; modint() :n(0) { ; } modint(ll m) :n(m) { if (n >= mod)n %= mod; else if (n < 0)n = (n%mod + mod) % mod; } operator int() { return n; } }; bool operator==(modint a, modint b) { return a.n == b.n; } modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; } modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; } modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; } modint operator+(modint a, modint b) { return a += b; } modint operator-(modint a, modint b) { return a -= b; } modint operator*(modint a, modint b) { return a *= b; } modint operator^(modint a, int n) { if (n == 0)return modint(1); modint res = (a*a) ^ (n / 2); if (n % 2)res = res * a; return res; } ll inv(ll a, ll p) { return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p); } modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); } const int max_n = 2050; modint fact[max_n], factinv[max_n]; void init_f() { fact[0] = modint(1); for (int i = 0; i < max_n - 1; i++) { fact[i + 1] = fact[i] * modint(i + 1); } factinv[max_n - 1] = modint(1) / fact[max_n - 1]; for (int i = max_n - 2; i >= 0; i--) { factinv[i] = factinv[i + 1] * modint(i + 1); } } modint comb(int a, int b) { if (a < 0 || b < 0 || a < b)return 0; return fact[a] * factinv[b] * factinv[a - b]; } struct uf { private: vector par, ran; public: uf(int n) { par.resize(n, 0); ran.resize(n, 0); rep(i, n) { par[i] = i; } } int find(int x) { if (par[x] == x)return x; else return par[x] = find(par[x]); } void unite(int x, int y) { x = find(x), y = find(y); if (x == y)return; if (ran[x] < ran[y]) { par[x] = y; } else { par[y] = x; if (ran[x] == ran[y])ran[x]++; } } bool same(int x, int y) { return find(x) == find(y); } }; int dx[4] = { 0,1,0,-1 }; int dy[4] = { 1,0,-1,0 }; ll gcd(ll a, ll b) { if (a < b)swap(a, b); while (b) { int r = a % b; a = b; b = r; } return a; } void solve() { int n; cin >> n; vector a(n); ll g = 0; rep(i, n) { cin >> a[i]; if (a[i] >= 0) { g = gcd(g, a[i] * a[i]); } } if (g == 0)g = -1; cout << g << endl; } signed main() { ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(10); //init_f(); //init(); //init(); //int t; cin >> t; rep(i, t)solve(); //while(cin>>w>>h,w)solve(); solve(); stop return 0; }