#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

long long gcd( long long a, long long b ) {
    
    if ( b == 0 ) { return a; }
    
    gcd( b, a%b );
    
}

int main() {
    
    long long N,D;
    cin >> N >> D;
    
    if ( N == D ) { cout << 0 << endl; return 0; }
    
    cout << N / gcd(N,D) -1 << endl;
    
    
    return 0;
}