#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

long long n,i,j,st,dr,m;
int gasit;

int nr_zero(long long x)
{
    int nr=0;
    while (x)
    {
        nr+=x/5;
        x=x/5;
    }
    return nr;
}

int main()
{
    f>>n;
    if (n==0)
        g<<1;
    else
    {
        st=1;
        dr=999999999;
        gasit=0;
        while (st<=dr && gasit==0)
        {
            m=(st+dr)/2;
            if (nr_zero(m)<n)
                st=m+1;
            else
                if (nr_zero(m)>n)
                    dr=m-1;
                else
                    gasit=1;
        }
        if (gasit==1)
        {
            while (nr_zero(m)==n)
                m--;
            g<<m+1;
        }
        else
            g<<-1;
    }
    return 0;
}