Problem:
Score : 100 points

Problem Statement

We will buy a product for N yen (the currency of Japan) at a shop.

If we use only 1000-yen bills to pay the price, how much change will we receive?

Assume we use the minimum number of bills required.

Constraints

1 \leq N \leq 10000

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the amount of change as an integer.

Sample Input 1

1900

Sample Output 1

100

We will use two 1000-yen bills to pay the price and receive 100 yen in change.

Sample Input 2

3000

Sample Output 2

0

We can pay the exact price.

Solution in C (Clang 10.0.0) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(){
	int N;
	int a;
	int b;
	int c;
	int d;
	
	scanf("%d",&N);
	if(1<=N<=10000){
		a=1000;
		d=N%1000;
		
		if(d=0){
		c=N/1000;
		b=N-a*c;
		}else{
			c=N/1000+1;
			b=N-a*c;
		}
		if(b<0) b=-1*b;
		
	}
		
		printf("%d\n",b);
	return 0;
	
}