Fox Ciel just used the command "sudo" (super-user do) to gain administrative privileges in the UNIX-based operating system on her computer. She now wants to install several new programs. Each program has some dependencies: in addition to the program, the package manager has to install some libraries used by the program. The package repository contains exactly 1000 libraries. For simplicity, we will number them from 1 to 1000, inclusive. You are given the information about the dependencies of the programs Fox Ciel wants to install. More precisely, you are given the s A and B, both containing the same number of elements. For each valid i, one of the programs needs all libraries that have numbers between A[i] and B[i], inclusive. Note that the programs may have overlapping dependences: multiple programs may require the same library to be installed. Of course, in such cases it is sufficient to install such a library once. Calculate and return the total number of libraries that need to be installed.
how to solve
I use "imosu-ho"