class FenwickTree: def __init__(self, size): self.n = size self.tree = [0] * (self.n + 1) def add(self, index, delta): index += 1 while index <= self.n: self.tree[index] += delta index += index & -index def sum(self, index): index += 1 res = 0 while index > 0: res += self.tree[index] index -= index & -index return res L=10**6 f=[[] for i in range(L+1)] for i in range(1,L+1): for j in range(i,L+1,i): f[j]+=[i] f[i]=f[i][-2:]