#include <iostream>
#include <fstream>
using namespace std;

int solve(int x , int y){
    int i,nr=1,k=1;

    if(x%y==0 || y%x==0)
            return -1;
    else{
        for(i=2;i<y;i++)
            nr++;
        for(i=1;i<nr;i++){
        k=x*k;
        }
        return k%y;
    }
}
int main()
{
    ifstream f("inversmodular.in");
    ofstream g("inversmodular.out");
    int x,y;
    f>>x>>y;
    g<<solve(x , y);
    return 0;
}