Trees were planted in a square shape in the open field. If 5 trees are planted per side, how many trees should be planted?
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))