#include<bits/stdc++.h>
using namespace std;
using ll = long long;

ll lowbit(ll x)
{
	return x & -x;
}

int main()
{
	ll n;
	cin>>n;
	n --;
	if(n == lowbit(n))
	{
		puts("1");
	}
	else
	{
		puts("impossible");
	}
	return 0;
}