#include <fstream>
#include <stdio.h>

using namespace std;

int main()
{
    int n=1,p,ok=0,s=0,ok1=0,cont=0;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    if(p%6==5)
    g<<"-1";
    else
    g<<(p-(p/6))*5;
}