https://blog.csdn.net/csyifanZhang/article/details/106128211

↑详细题解

#define ll int
#define inf 0x3f3f3f3f
#define MAX 55
#define vec vector<ll>
#define P pair<ll,ll>

//dp[j]:凑出j需要的最小邮票数目
int K, N, a[MAX], dp[2000005];

int main() {
	
	while (cin >> K >> N) {
		memset(dp, 0, sizeof(dp));
		ll maxx = 0;
		for (int i = 1; i <= N; i++)cin >> a[i];
		sort(a + 1, a + N + 1);//一定要排序
		int i = 0;
		while (dp[i] <= K) {
			i++; dp[i] = inf;
			for (int j = 1; j <= N && a[j] <= i; j++)
				dp[i] = min(dp[i], dp[i - a[j]] + 1);
		}
		cout << i - 1 << endl;
	}
}