#include <iostream>
using namespace std;

int main() {
	int M, K, value[1005], dp[1005] = {0};
	while(cin >> M) {
		if(M == 0) break;
		cin >> K;
		for(int i = 0;i < K;i++)
			cin >> value[i];
		for(int i = 1;i <= M;i++) {
			dp[i] = 999999;
			for(int j = 0;j < K;j++) {
				if(i >= value[j]) {
					dp[i] = min(dp[i-value[j]]+1, dp[i]);
				}
			}
		}
		if(dp[M] == 999999) cout << "Impossible" << endl;
		else cout << dp[M] << endl;
	}
	return 0;
}