#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int main()
{
   long long int p, s, s1, x,i,t,ok;
   in>>p;
   x=1;
   for(i=1;i<=30;i++) x=x*2;
   t=0; i=64; s=0;
   while(i!=0)
   {
                     s=t+i; s1=0;
                     while(s!=0)
                     {
                                s1=s1+(s/5);
                                s=s/5;
                     }
                     if(s1<p)
                     {
                             t=t+i;
                     }
                     i=i/2;
   }
   ok=1;
   while (ok)
   {
      s=t; s1=0;
      while(s!=0)
     {
            s1=s1+(s/5);
            s=s/5;
     }
     if(s1==p)
     {
        ok=0;
        out<<t;
        break;

     }
    t++;
   }
  return 0;
}