#include <iostream>
#include <map>

int main(int argc, char *argv[]) {
	std::map<int, int> valid_map({
		{1, 0},
		{2, 0},
		{3, 0},
		{4, 0},
		{5, 0},
		{6, 0},
		{7, 0},
		{8, 0},
		{9, 0},
		{10, 0}
	});
	int input;
	while (std::cin >> input) {
		valid_map.erase(input);
	}

	auto map_iter = valid_map.begin();
	std::cout << map_iter->first << std::endl;
	return 0;
}