#include <iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int p, n=1,cate,cn,sol;
int main()
{f>>p;
do{n++;
   cn=n;
   while(cn%5==0)cate++,cn/=5;
   if(cate>=p)sol=n;
  }while(cate<p);
  g<<sol;
}