#include <stdio.h>
#include <math.h>
long long p;
long nr_cf(long a)
 {
  long nr5=0;
  for ( long i=5;i<=a;i+=5)
      {
        long j=i;
       while ((j%5==0)&&(j!=0))
	  {
	   j/=5;
	   nr5++;
	  }
      }
  return nr5;
 }
void verificare (double a)
 {
  int i=int(a);
  while (nr_cf(i-1)==p)
    i--;
  printf("%d",i);
 }
void caut_bin(long x, long y)
 {
  long s=(x+y)/2;
  long long k=nr_cf(s);
  if (k<p)
  {
		caut_bin(s,y);
		return;
  }
    
  if (k>p)
  {
		caut_bin(x,s);
		return;
  }
  if (k==p)
	  verificare(s);
 }
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%lld",&p);
	caut_bin(1,2000000000);
	fclose(stdout);
	return 0;
}