#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>

int main()
{
	long long int maney = 0;
	int children = 0;
	int divisionManey = 0;
	int giveManey = 0;

	scanf("%d", &maney);
	scanf("%d", &children);

	divisionManey = maney / children;

	if (divisionManey < 1000)
	{
		printf("0\n");
		return 0;
	}

	while (divisionManey > 1000)
	{
		giveManey += 1000;
		divisionManey -= 1000;
	}

	printf("%d\n", giveManey);
}