In the fall semester, X of the NTHU 2020 Computer Science majors take the course CS13550* Introduction to Programming (I), Y of them take the course CS13570* Introduction to Computer Systems and Applications, and Z of them take both of the two courses. How many NTHU 2020 CS majors are there in total?
Three integers X, Y, Z which are separated by blanks. Note that 0<X<1000, 0<Y<1000, and 0<Z<1000.
One integer which denotes the number of all the NTHU 2020 CS majors. Note that you don't need to print '\n' at the end of the output.