#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

long gcd(long m, long n) {
  if (m < n) swap(m, n);
  long r = m % n;
  if (!r)
    return n;
  else {
    m = n;
    n = r;
    return gcd(m, n);
  }
}
long lcm(long m, long n) {
	return (m * n / gcd(m, n));
}

int main(void) {
#ifdef DEBUG
  freopen("input.txt", "r", stdin);
#endif

  ios_base::sync_with_stdio(false);
  cin.tie(NULL);

  long N, D, ans;
  cin >> N >> D;

  ans = lcm(N, D) / D - 1;
  cout << ans << endl;
  return 0;
}