Some flight requires more than 15 people to depart. If there are 9 people currently on the plane, find how many more people need to board before departure.
15 1 [OP_ADD] 9 [OP_SUB]
var_a = 15
var_b = 1
var_c = var_a + var_b
var_d = 9
var_e = var_c - var_d
print(int(var_e))