Problem:
Score : 100 points

Problem Statement

You went shopping to buy cakes and donuts with X yen (the currency of Japan).

First, you bought one cake for A yen at a cake shop.
Then, you bought as many donuts as possible for B yen each, at a donut shop.

How much do you have left after shopping?

Constraints

1 \leq A, B \leq 1 000

A + B \leq X \leq 10 000

X, A and B are integers.

Input

Input is given from Standard Input in the following format:

X
A
B

Output

Print the amount you have left after shopping.

Sample Input 1

1234
150
100

Sample Output 1

84

You have 1234 - 150 = 1084 yen left after buying a cake.
With this amount, you can buy 10 donuts, after which you have 84 yen left.

Sample Input 2

1000
108
108

Sample Output 2

28

Sample Input 3

579
123
456

Sample Output 3

0

Sample Input 4

7477
549
593

Sample Output 4

405

Solution in Python (3.4.3) (judge verdict: Runtime Error)

#例題4
A = int(input())
B = int(input())
C = int(input())
X = int(input())
if A>50 or B>50 or C>50 or X<50 or X>20000 or X % 50 != 0:
    pass
else:
    x = X // 50
    #print(x)
    y = 0
    xA = x // 10
    xB = (x - xA * 10) //2
    xC = x - xA * 10 - xB * 2
    #print(str(xA)+', '+str(xB)+', '+str(xC))
    if xA <= A:
        while xA >= 0: #and xB <= B:
            #print(str(xA)+', '+str(xB)+', '+str(xC))
            if xB <= B:
                yB = xB
                yC = xC
                while yB >= 0 and yC <= C:
                    #print(str(yB)+', '+str(yC))
                    yB = yB - 1
                    yC = yC + 2
                    y = y + 1
                xA = xA -1
                xB = xB + 5
            else:
                yB = B
                yC = x - xA * 10 - yB * 2
                if yC <= C:
                    while yB >= 0 and yC <= C:
                        #print(str(yB)+', '+str(yC))
                        yB = yB - 1
                        yC = yC + 2
                        y = y + 1
                    xA = xA -1
                    xB = xB + 5
                

    else:
        xA = A
        xB = (x - xA * 10)//2
        if xB <= B:
            y = 0
            while xA >= 0: #and xB <= B:
                print(str(xA)+', '+str(xB)+', '+str(xC))
                if xB <= B:
                    yB = xB
                    yC = xC
                    while yB >= 0 and yC <= C:
                        #print(str(yB)+', '+str(yC))
                        yB = yB - 1
                        yC = yC + 2
                        y = y + 1
                    xA = xA -1
                    xB = xB + 5
                else:
                    yB = B
                    yC = x - xA * 10 - yB * 2
                    if yC <= C:
                        while yB >= 0 and yC <= C:
                            #print(str(yB)+', '+str(yC))
                            yB = yB - 1
                            yC = yC + 2
                            y = y + 1
                        xA = xA -1
                        xB = xB + 5
        else:
            xB = B
            xC = (x - xA * 10 - yB * 2)
            y = 0
            while xA >= 0 and xB <= B:
                #print(str(xA)+', '+str(xB)+', '+str(xC))
                yB = xB
                yC = x - xA * 10 - yB * 2
                while yB >= 0 and yC <= C:
                    #print(str(yB)+', '+str(yC))
                    yB = yB - 1
                    yC = yC + 2
                    y = y + 1
                xA = xA -1
                xB = xB + 5
                    
print(y)