P6962
Alice 选择n个正整数 a1,a2,...,ana_1,a_2,...,a_na1,a2,...,an "满足ai≤∑j=1i−1aj a_i\le \sum\limits_{j=1}^{i-1} a_jai≤j=1∑i−1aj"
大小关系打反了吧,应该是大于。