#include <iostream>
#include <algorithm>
using namespace std;
int a[150000000];
int main(void) {
  int N, D, c = 0, j = 0;
  cin.tie(0);
  cin >> N >> D;
  a[j++] = 1;
  for (int i = 1+D;; i+=D) {
    if (i <= N) {
      if(!(count(a, a+j, i))) {
	c++;
	a[j++] = i;
      } else {
	break;
      }
    } else {
      i-=N;
      if(!(count(a, a+j, i))) {
	c++;
	a[j++] = i;
      } else {
	break;
      }
    }
  }
  cout <<c<<endl;
  return 0;
}