#include <iostream>
#include <algorithm>
using namespace std;

typedef long long ll;

ll gcd(ll x, ll y) {
  if (x < y) swap(x, y);
  int tmp;
  while (y) {
    tmp = y;
    y = x % y;
    x = tmp;
  }
  return x;
}

ll lcm(ll x, ll y) {
  if (x < y) swap(x, y);
  return (x * y / gcd(x, y));
}

int main(void) {
  int N, D;
  cin.tie(0);
  cin >> N >> D;

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