#include <fstream>

using namespace std;

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

int verif (int n)
{
    short int fact=5;
    int cnt=0;
    while(fact<=n)
    {
        cnt+=n/fact;
        fact*=5;
    }
    return cnt;
}

int main()
{
    long long p,st=1,dr=50000000,m,q;
    in>>p;
    while(st<=dr)
    {
        m=(st+dr)/2;
        q=verif(m);
        if(m<p)
            st=m+1;
        else if(m>p)
            dr=m-1;
        else
        {
            out<<m-m%5;
            return 0;
        }
    }
    out<<-1;
    return 0;
}