AmazonOA #1
System Vulnerabilities
估计困难可在线判题
The vulnerability of each non-empty contiguous segment is its length multiplied by its maximum element. Find the sum of the vulnerabilities of all contiguous segments, modulo 1000000007.
输入格式
The first line contains n (1..100000); the second line contains n vulnerability values (1..10⁹).
输出格式
Output one integer, the answer required by the problem.
样例 1
输入:
3
3 1 4
输出:
34
样例 2
输入:
2
2 2
输出:
8
样例 3
输入:
1
1
输出:
1
样例说明
Example 1: the six contiguous segments contribute 3, 6, 12, 1, 8 and 4 in order, for a total of 34. Example 2: the two single-element segments contribute 2 each, and the whole segment contributes 2×2=4, for a total of 8. Example 3: the only segment contributes 1.