
65  ZOJ Monthly, May 2008  1007
There are n stacks, named in order S[1], S[2], S[3], ... ,S[n]. Initially, all of them are empty. The following process ends when S[n] is full. If non of the stacks is full, S[1] is filled by numbers 1, 2, 3, ... in order until it's full. Else, there is a full stack S[i], it is poped and pushed into S[i+1] until S[i] is empty or S[i+1] is full, whichever comes first. If S[i+1] is full and there are numbers in S[i], the numbers in S[i] are poped away. Input There are multiple test cases. There are three lines for each case. The first line is an integer N (1 <= N <= 1,000), the number of stacks. The second line is N integers: C_{1} C_{2} ... C_{N} , in which C_{i} (1 <= C_{i} <= 1,000,000,000) is the size of ith stack. The third line is two integers X and Y (1 <= X <= Y <= C_{N} ). Process to the end of file. Output For each case, print a number in one line, the sum of the numbers in S[n] from index X to Y. The index starts from 1 at the bottom of a stack. The result will fit in a signed 64bit integer. Sample Input
1 100 1 100 2 2 4 1 3 3 5 3 5 3 4 Sample Output
5050 5 8 Author: GAO, Yuan 