USACO：Humble Numbers

/*ID: Jang LawrencePROG: humbleLANG: C++*/#include<iostream>#include<cstring>#include<cstdio>#include<string>#include<algorithm>#include<queue>#include<set>#include<cmath>#include<climits>#define X first#define Y second#define sqr(a) ((a)*(a))using namespace std;typedef long long lng;int k,n;int s[111];set<int> q;int main(){  #ifndef  DEBUG  freopen("humble.in","r",stdin);  freopen("humble.out","w",stdout);  #endif  scanf("%d%d",&k,&n);  for(int i=0;i<k;++i)  {scanf("%d",s+i);q.insert(s[i]);}  for(int i=0;i<k;++i)  {      set<int>::iterator it=q.begin();      while(1)      {          int t=(*it)*s[i];          if(t<0) break;          if(q.size()>n)          {              q.erase(--q.end());              if(t>=*(--q.end())) break;          }          q.insert(t);          ++it;      }  }  printf("%d\n",*(--q.end()));    return 0;}