[codeforces] A. Soldier and Bananas

A soldier wants to buy w bananas in the shop. He has to pay k dollars for the first banana, 2k dollars for the second one and so on (in other words, he has to pay i·k dollars for the i-th banana).

He has n dollars. How many dollars does he have to borrow from his friend soldier to buy w bananas?

 

Input

The first line contains three positive integers k, n, w (1  ≤  k, w  ≤  1000, 0 ≤ n ≤ 109), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.

 

Output

Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn't have to borrow money, output 0.

 

Using language : python3 

 

def solution(userinput_list):
    answer_sum = 0
    for check in range(0,int(userinput_list[2])):
        answer_sum += int(userinput_list[0]) * (check+1)
    return answer_sum - int(userinput_list[1])

if __name__ == "__main__":

    input1 = list(input().split(" "))
    if solution(input1) <= 0 :
        print("0")
    else:
        print(solution(input1))