There are 120 liters (L) of water in the water tank. When you open the faucet in this water tank, 4 liters (L) of water flow out per minute. How many liters (L) of water are left in the water tank after 20 minutes you open the faucet?
120 4 20 [OP_MUL] [OP_SUB]
var_a = 120
var_b = 4
var_c = 20
var_d = var_b * var_c
var_e = var_a - var_d
print(int(var_e))