#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream be("pascal.in");
    ofstream ki ("pascal.out");
    long r; int d;
    be >> r; be >> d;
    long long s = r;
    long i = 1;
    while ((s % d)!=0) {
        i++;
        s = s * (r-i+1) / i;
    }

    ki << r - 2*i + 1;
    be.close(); ki.close();
    return 0;
}