#include <stdio.h>
#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <stack>
#include <algorithm>
#include <iomanip>
#include <map>
#include <queue>
#include <functional>
#include <numeric>
#include <chrono>
#include <cstdlib>
using ll = long long;
using namespace std;

const ll MOD = 1e9 + 7;
#define REP(i, n) for (int(i) = 0; (i) < (n); ++(i))
#define repi(i, a, b) for (int i = int(a); i < int(b); ++i)
// bool operator<(const pair<int, int> &a, const pair<int, int> &b)
// {
//     if (a.first == b.first)
//         return a.second < b.second;
//     return a.first < b.first;
// };

/*unsigned int xor128(void)
{
    static unsigned int x = 123456789, y = 362436069, z = 521288629, w = 88675123;
    unsigned int t = (x ^ (x << 11));
    x = y;
    y = z;
    z = w;
    return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
unsigned int xor128rnd(unsigned int m)
{
    return xor128() % m;
}*/

/*bool operator<(const pair<int, int> &a, const pair<int, int> &b)
{
    if (a.first == b.first)
    {
        return a.second < b.second;
    }
    return a.first < b.first;
}*/
set<ll> st;
int main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll N, D;
    cin >> N >> D;

    if (D == 1)
    {
        cout << N - 1 << endl;
        return 0;
    }
    int pos = 0;
    st.insert(pos);
    while (1)
    {
        pos = (pos + D) % N;
        if (st.find(pos) != st.end())
            break;
        st.insert(pos);
    }
    cout << st.size() - 1 << endl;
    return 0;
}