Woong, Youngsoo, and Hyogeun each had a few marbles. In turn, Woong gave Youngsu 5 marbles, Youngsu gave Hyogeun 10 marbles, and Hyogeun gave Woong 7 marbles, so that all three of them have 20 marbles each. Find the number of marbles Woong had at first.
20 7 [OP_SUB] 5 [OP_ADD]
var_a = 20
var_b = 7
var_c = var_a - var_b
var_d = 5
var_e = var_c + var_d
print(int(var_e))