#include<iostream>
#include<vector>

using namespace std;

int FindIndex(int n)
{
    if(n<=2)
    return -1;
    if(n%2==1)
    return 2;
    if(n%4==0)
    return 3;
    return 4;
}

int main()
{
    int n;
    while(cin>>n)
    {
        int res=FindIndex(n);
        cout<<res<<endl;
    }
    return 0;
}