// MagicDark
#include <bits/stdc++.h>
#define debug cerr << "[" << __LINE__ << "] "
#define SZ(x) (int) x.size() - 1
#define all(x) x.begin(), x.end()
#define ms(x, y) memset(x, y, sizeof x)
#define F(i, x, y) for (int i = (x); i <= (y); i++)
#define DF(i, x, y) for (int i = (x); i >= (y); i--)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> inline void chkmax(T& x, T y) { x = max(x, y); }
template <typename T> inline void chkmin(T& x, T y) { x = min(x, y); }
template <typename T> inline void read(T &x) {
	x = 0; int f = 1; char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
	for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
	x *= f;
}
bool t[15];
int gcd(int x, int y) { return y ? gcd(y, x % y) : x; }
bool check(int x) {
	if (x == 1) return false;
	for (int i = 2; i * i <= x; i++)
		if (x % i == 0) return false;
	return true;
}
signed main() {
	int x; read(x);
	ms(t, true);
	while (x--) {
		int y; read(y);
		t[y] = false;
	}
	if (t[2]) {
		puts("2");
		return 0;
	}
	if (t[3]) {
		puts("3");
		return 0;
	}
	if (t[5]) {
		puts("5");
		return 0;
	}
	if (t[7]) {
		puts("7");
		return 0;
	}
	// bool flag = 
	// F(i, 0, 9)
	int g = 0;
	F(i, 0, 9)
		if (t[i]) g = gcd(g, i);
	if (g != 1) {
		puts("-1");
		return 0;
	}
	queue <int> q;
	F(i, 0, 9)
		if (t[i] && i) q.push(i);
	while (q.size()) {
		int x = q.front(); q.pop();
		if (check(x)) {
			cout << x;
			return 0;
		}
		F(i, 0, 9)
			if (t[i]) q.push(x * 10 + i);
	}
	return 0;
}
/* why?
*/