#include <iostream>
#include <vector>

constexpr int BITS = 64;

void get_ones(std::vector<int>& ones){
	unsigned long long num;

	std::cin >> num;

	int i = 0;
	while (num){
		ones[i] += num & 1;
		num >>= 1;
		i++;
	}
}

int main() {
	int n = 0;

	std::cin >> n;

	std::vector<int> ones(BITS);

	for (int i = 0; i < n; i++){
		get_ones(ones);
	}
	

	bool pr = false;
	unsigned long long mask = 1;
	unsigned long long num = 0;
	bool set = false;
	for (int i = 0; i < BITS; i++){
		set = false;
		if (ones[i] >= 2) {
			pr = true;	
			set = true;
		} else if (ones[i] == 1 && pr){
			pr = true;
			set = true;
		} else if (ones[i] == 0 && pr){
			set = true;
			pr = false;
		} else if (ones[i] > 0){
			set = true;
		}
		if (set) {
			num |= mask;	
		}
		mask <<= 1;
	}
	std::cout << num << '\n';
	//for (auto& one: ones){
	//	std::cout << one;
	//}
	//std::cout << '\n';
	return 0;

}