You are trying to make a square fence with 5 stakes per side. Find how many stakes you will need.
5 4 [OP_MUL] 4 [OP_SUB]
var_a = 5
var_b = 4
var_c = var_a * var_b
var_d = 4
var_e = var_c - var_d
print(int(var_e))