#include <iostream>
#include <fstream>

using namespace std;

ifstream fin ("fact.in");
ofstream fout ("fact.out");

int main()
{
    int P,n,contor,i,ci,k;
    fin>>P;
    contor=0;
    i=5;
    while (contor<P)
    {
        if (k%5==0)
            contor++;
        contor++;
        k++;
        i+=5;
    }
    if (contor==P)
        fout<<i-5;
    else
        fout<<-1;
    return 0;
}