cf 990A

#include<stdio.h>

int main()
{
    long long n, m;
    int a, b;
    scanf("%lld %lld %d %d", &n, &m, &a, &b);

    if(a * (m - (n % m)) > b * (n % m)) printf("%lld\n", b * (n % m));
    else printf("%lld\n", a * (m - (n % m)));
}