#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    int i,p,n,contor=0,aux;
    fstream f("factorial.in",ios::in);
    f>>p;f.close();
    i=1;
    while(contor<p)
    {
      aux=i;
      while(aux%5==0)
      {
         aux/=5;
         contor++;
         }
         i++;
    }
    i--;
    fstream g("factorial.out",ios::out);
    g<<i;
    g.close();
}