#include <cmath>
#include <vector>
#include <map>
#include <functional>
#include <queue>
#include <iostream>
#include <string>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <cstdint>
#include <climits>
#include <unordered_set>

using namespace std;

#define ll long long int
#define ti4 tuple<int,int,int,int>
#define pii pair<ll,ll>
#define REP(x,n) for(int x = 0;x < n;x++)

template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}

struct UnionFind {
    vector<int> data;
    UnionFind(int size) : data(size, -1) { }
    bool unionSet(int x, int y) {
        x = root(x); y = root(y);
        if (x != y) {
            if (data[y] < data[x]) swap(x, y);
            data[x] += data[y]; data[y] = x;
        }
        return x != y;
    }
    bool findSet(int x, int y) {
        return root(x) == root(y);
    }
    int root(int x) {
        return data[x] < 0 ? x : data[x] = root(data[x]);
    }
    int size(int x) {
        return -data[root(x)];
    }
};

const ll mod = (ll)(1e9+7);

struct SimpleHash {
    size_t operator()(const std::pair<ll, ll>& p) const {
        return p.first * mod + p.second;
    }
};

ll gcd( ll m, ll n )
{
    if ( ( 0 == m ) || ( 0 == n ) )
        return 0;
    
    while( m != n )
    {
        if ( m > n ) m = m - n;
        else         n = n - m;
    }
    return m;
}

ll lcm( ll m, ll n )
{
    if ( ( 0 == m ) || ( 0 == n ) )
        return 0;
    
    return ((m / gcd(m, n)) * n);
}

int main()
{
    ll n, d;
    cin >> n >> d;
    
    if(d > n)
    {
        d = d % n;
    }
    if(d == 0)
    {
        cout << 0 << endl;
        return 0;
    }
    if(n == d)
    {
        cout << 0 << endl;
        return 0;
    }
    ll l = lcm(d, n);
    cout << (l / d) - 1 << endl;
    return 0;
}