#include<iostream>

using namespace std;

int Getpos(int line,int num)
{
    if(num<1 || num>2*line-1)
        return 0;
    else if(num==1 || num==2*line-1)
        return 1;
    else
        return Getpos(line-1,num-2)+Getpos(line-1,num-1)+Getpos(line-1,num);
        
}

int run(int x)
{
    int tmp;
    for(int i=1;i<=x;i++)
        if(Getpos(x,i)%2==0)
            return i;
    return -1;
}

int main()
{
    int t;
    cin >>t;
    cout << run(t);
    return 0;
}