#include <fstream>
using namespace std;



int main()
    {
    long long h,x,p;
    int gr;
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>p;
    x=p;
    h=1;
    gr=0;
    if(p>=1)
        {
        while(h*5+1<=p)
            {
            h=(h*5)+1;
            gr++;
            }
        if(((p+gr)%h)<gr)
            fout<<"-1"<<"\n";
        else
            {
            while(h!=1)
                {
                x-=(x/h);
                h--;
                h=h/5;
                }
            fout<<x*5;
            }
        }
    else
        if(p==0)
            fout<<-1;

    fout<<"\n";
    fin.close();
    fout.close();
    return 0;
    }