#755. Pairs with sum k
Count the pairs with i < j and a[i] + a[j] = k.
### Input
The first line has n, the second line has n integers separated by spaces. The third line has k.
### Output
A number.
Examples
Input
6 10 10 4 7 9 0 9
Output
1
Input
10 3 2 2 8 8 1 6 2 6 7 3
Output
3
💡 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.