#include <iostream>
#include <fstream>
#include <vector>
#include <set>
#include <algorithm>
#include <unordered_map>

using namespace std;

ifstream input_stream;
ofstream output_stream;


int getMinRest(int L, int lengths[], int K) {
	for (int i = 0; i < K; i++) {
		if (L % lengths[i] == 0) {
			return 0;
		}
	}

	sort(lengths, lengths + K);
	for (int i = 1; i < K; i++) {
		if (lengths[i] - lengths[i - 1] == 1 && lengths[i] * lengths[i - 1] < L) {
			return 0;
		}
	}

	if (K < 2) {
		return L % lengths[0];
	}


	set<int> processed_lengths;
	set<int> new_lengths;
	unordered_map<int, bool> detected_lengths;

	for (int i = 0; i < K; i++) {
		processed_lengths.insert(lengths[i]);
		new_lengths.insert(lengths[i]);
		detected_lengths[lengths[i]] = true;
	}

	while (true) {
		// cout << "Processed: " << processed_lengths.size() << "; New: " << new_lengths.size() << endl;
		set<int> found_lengths;

		for (auto i: processed_lengths) {
			for (auto j: new_lengths) {
				int new_len = i + j;
				if (new_len <= L && detected_lengths[new_len] == false) {
					found_lengths.insert(new_len);
					detected_lengths[new_len] = true;
				}
			}
		}

		processed_lengths.insert(new_lengths.begin(), new_lengths.end());
		if (found_lengths.size() == 0) {
			break;
		}
		new_lengths = found_lengths;
	}

	auto m = processed_lengths.end();
	m--;
	return L - *m;
}



int main() {
	input_stream.open("input.txt");

	int L, K;
	input_stream >> L;
	input_stream >> K;

	int lengths[K];
	for (int i = 0; i < K; i++) {
		input_stream >> lengths[i];
	}

	cout << getMinRest(L, lengths, K) << endl;

	input_stream.close();
	return 0;
}