#758. Triples with sum 0
Count the triples with i < j < l and a[i] + a[j] + a[l] = 0.
### Input
The first line has n, the second line has n integers separated by spaces.
### Output
A number.
Examples
Input
11 2 5 -1 -5 -4 1 1 3 -3 3 -3
Output
11
Input
9 -3 2 -2 3 4 1 3 5 3
Output
2
💡 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.