#include <stdio.h>
int main()
{
int p,i,supergenial;
unsigned long  n,emi;
FILE *fin, *fout;
fin=fopen("fact.in","r");
scanf("%d",&p);
n=1;
i=1;
z=0;
supergenial=0;
while (supergenial!=p)
 {
 n*=i;//calculeaza factorialul
 i++;
 emi=n;//salvez valoarea lui n pt a nu se pierde
 k=0;

	while (emi%5==0)
	{emi=emi/5;
	supergenial++;}

 supergenial=0;
}
  fclose(fin);
  fout=fopen("fact.out","w");
  if (supergenial==p) fprintf(fout,"%d",i);
  else fprintf(fout,"-1");
  fclose(fout);
  return 0;
}