#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long inf = (long long)1e17;
const long double eps = 1e-12;
const long long N = (int)1e5 + 5;
const long long LOGN = 19;
const long double PI = 3.14159265358979323846;
long long mul(long long a, long long b, long long m = mod) {
  return (long long)(a * b) % m;
}
long long add(long long a, long long b, long long m = mod) {
  a += b;
  if (a >= m) a -= m;
  if (a < 0) a += m;
  return a;
}
long long power(long long a, long long b, long long m = mod) {
  if (b == 0) return 1;
  if (b == 1) return (a % m);
  long long x = power(a, b / 2, m);
  x = mul(x, x, m);
  if (b % 2) x = mul(x, a, m);
  return x;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  if (0) {
    freopen("C:\\Users\\Dishant\\Desktop\\Collection-DEV c++\\input.txt", "r",
            stdin);
    freopen("C:\\Users\\Dishant\\Desktop\\Collection-DEV c++\\output.txt", "w",
            stdout);
  }
  long long n, m, a, b;
  cin >> n >> m >> a >> b;
  long long rem = n % m;
  if (rem == 0) {
    cout << "0\n";
    return 0;
  } else {
    long long times = n / m;
    long long A = (times + 1LL) * m - n;
    cout << min((long long)rem * b, (long long)A * a) << endl;
  }
  return 0;
}
