#include <fstream>

using namespace std;

int main()
{
    unsigned long int p,l;
    long m,i,r;
    ifstream f("fact.in");
    ofstream g("fact.out");

    f>>p;
    if(p==1)r=0;
    else{
        m=-1;
        i=-1;
        do{
            if(i==(m+30)){i++;m=i;continue;}
            l=i/5;
            i+=6;
        }while(i<p);
        if(i==-1)r=p*5;
        else{
            if(p==i)r=-1;
            else r=5*(p-l);
        }
    }
    g<<r;
    return 0;
}