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ZOJ Problem Set - 2962
Stack By Stack

Time Limit: 5 Seconds      Memory Limit: 32768 KB

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: C1 C2 ... CN , in which Ci (1 <= Ci <= 1,000,000,000) is the size of ith stack. The third line is two integers X and Y (1 <= X <= Y <= CN ).

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 64-bit 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
Source: ZOJ Monthly, May 2008
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