#942. Rain water
You get the heights of columns. After the rain, how many units of water stay trapped between them?
### Input
The first line has n, the second line has n integers separated by spaces.
### Output
A number.
Examples
Input
5 6 4 1 7 3
Output
7
Input
14 6 0 4 2 1 1 5 0 6 0 1 4 0 7
Output
48
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.