Balance of time-space efficiency: inverse pairs in arrays

In the array of two digits, if the previous number is greater than the number that follows, then these two numbers form an inverse pair. Enter an array to find the total number of reverse pairs in this array p. and the output of p to 1000000007 modulo is obtained. i.e. Output p%1000000007

Input Description:

The title guarantees that the input array does not have the same number

Data range:

For%50 data, size<=10^4

For%75 data, size<=10^5

For%100 data, size<=2*10^5

Input Example:

1,2,3,4,5,6,7,0

Output Example:

7

Balance of time-space efficiency: inverse pairs in arrays