遭受了普及-的智商碾压orz
其实就是说
两个人相遇后调头，
和互相穿过
完 全 等 价 啊
！！！
想到这一点就是入门-了吧

#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 5e3 + 10;
int n, l, a[maxn], ans1, ans2;
int main() {
  cin >> l >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + 1 + n);
  for (int i = 1; i <= n; i++) {
    ans1 = max(ans1, min(a[i], l - a[i] + 1));
    ans2 = max(ans2, max(a[i], l - a[i] + 1));
  }
  
  cout << ans1 << " " << ans2;
  return 0;
}