PAT 1038

#include 
#include 
#include 
using namespace std;
int N;
struct num {
	int sum=0;
	num* next[10] = { nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr };
	int end = 0;
};
num* nums = new num;
list res;
int getmin() {
	int res = 0;
	while (nums->next[res] == nullptr || nums->next[res]->sum <= 0) res++;
	return res;
}
int main() {
	cin >> N;
	getchar();
	for (int i = 0; i < N; i++)
	{
		int j = 0;
		char c;
		num* temp = nums;
		while ((c = getchar())!=' ' && c!='\n') {
			if (temp->next[c - '0'] == nullptr) temp->next[c - '0'] = new num;
			temp->next[c - '0']->sum++;
			temp = temp->next[c - '0'];
		}
		temp->end++;
	}
	num* temp = nums;
	nums->sum = N+1;
	while (nums->sum > 0) {
		temp->sum--;
		int i = 0;
		while (temp->next[i] == nullptr || temp->next[i]->sum <= 0) {
			i++;
			if (i==10) break;
		}
		if (temp->end != 0 && i != 10) {
			if (i > getmin()) {
				temp->end--;
				temp = nums;
			}
			else {
				res.push_back(i);
				temp = temp->next[i];
			}
		}
		else if (temp->end != 0) {
			temp->end--;
			temp = nums;
		}
		else if (i != 10) {
			res.push_back(i);
			temp = temp->next[i];
		}
	}
	while (!res.empty() && res.front() == 0) res.pop_front();
	if (res.empty()) cout << 0;
	for (auto it : res) cout << it;
	system("PAUSE");
	return 0;
}