#include <fstream>

using namespace std;
ifstream f ("fact.in");
ofstream g ("fact.out");
int nr,p,s,d,m;
int zero(int n)
{
    int nr=0,i;
    for(i=5;i<=n;i=i*5) nr=nr+n/i;
    return nr;
}
int main()
{
    f>>p;
    s=1; d=p*5;
    while(s<=d)
    {
        m=(s+d)/2;
        if(zero(m)>=p) d=m-1;
        else s=m+1;
    }
    if(zero(s)==p) g<<s;
    else g<<-1;
    return 0;
}