#include<stdio.h>
#include<math.h>
long int n,a,b,c;
long int h(long int x)
{
	return (long int)(log10(x)/log10(5));
}
long int binar(long int a,long int b)
{
	c=(a+b)/2;
	k=h(c);
	if(k==n) return c;
	else if(k<n) return binar(a,c-1);
	else return binar(c+1,b);
}
int main()
{
 FILE *in=fopen("fact.in","rt");
 fscanf(in,"%ld",&n);
 fclose(in);
  FILE *out=fopen("fact.out","wt");
  fprintf(out,"%ld",binar(1,1000000000));
  fclose(out);
 return 0;
}