#include<stdio.h>
int main()
{
FILE *fin,*fout;
fin = fopen("fact.in","r"); fout = fopen("fact.out","w");
long int n;
fscanf (fin,"%d",&n);
long int i=1,doi=0,cinci=0;
while (doi<n||cinci<n)
     {
     long int b=i;
     while (b%2==0)
	  {
	  doi++;b/=2;
	  }
     b=i;
     while (b%5==0)
	  {
	  cinci++;b/=5;
	  }
     i++;
     }
fprintf (fout,"%d",i-1);
fclose(fin);
fclose(fout);
return 0;
}