题目大意:给你一个n,a,b,k 有n+1个数据,让你求 ∑ni=0sian−ibi <munderover> ∑ i = 0 n </munderover> s i a n − i b i 答案取模1e9+9 条件是这n+1个数据每k个是一个循环 1<n,a,b<=1e9 1 < n , a , b <= 1 e 9 , 1<k<=1e5 1 < k <=...