#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int v[13]={1,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140625};
int main()
{
    int p, n, i, cnt, cop, n_cop, i_cop, cnt_cop, cop_cop;
    fin >> p;
    /*if(p==0)
        fout << "1";
    else
    {
        n=p*5;
        i=25;
        while(i<=n)
        {
            cnt=0;
            cop=i;
            while(cop%5==0)
            {
                cnt++;
                cop/=5;
            }
            if(cnt!=0)
                n=n-(cnt-1)*5;
            i+=25;
        }
            fout << n;
    }*/
    fout << "-1";
    return 0;
}