#include <fstream>
using namespace std;
long long p,divx,nrz,i,dr=10000000000LL,st,n,c;

long long nrzero( long long cif )
{
     long t = 0;
     while( cif )
     {
            t += cif/5;
            cif /= 5;
     }
     return t;
}
long long cautare(long long a, long long b)
{
     c=(a+b)/2;
     if(nrzero(c)==p) return c;
     if(nrzero(c) < p ) cautare( c+1 ,b);
     else cautare(a,c-1);
     return c;
     
     }
     
     
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;   
i=cautare(st,dr);
  g<<i;
    
    return 0;}