#include <stdio.h>

FILE *f,*g;
long i;
char ok;
long n,temp;

long calcp5(long x)
{
  long k,contor;
  k=5;
  contor=0;
  while(x%k==0)
    {
	  contor++;
	  k*=5;
	}
  return contor;
}

int main()
{
  f=fopen("fact.in","r");
  g=fopen("fact.out","w");
  fscanf(f,"%ld\n",&n);
  i=5;
  ok=0;
  while((i<=1000000000)&&(!ok))
	{
	  temp+=calcp5(i);
	  if(temp>=n) ok=1;
	  else i+=5;
	}
  if(!ok)
	fprintf(g,"-1\n");
  else
	fprintf(g,"%ld\n",i);
  fclose(f);   fclose(g);
  return 0;
}