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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(void){
int a, b, c, d , e, f;
    printf("X\n");
    printf("A\n");
    printf("B\n");
scanf("%d%d%d",&a,&b,&c);
if( a< b){
    printf("何も買えませんでした\n");
}
    else if(a >= b){
    d=(a-b)/c;//どーなつを買える個数
    if(d<1){
        e=a-b;
        printf("%d\n",e);
    }
    else if(d>=0){
        e=a-b-d*c;
        printf("%d\n",e);
}
}
    return(0);
}