#include<stdio.h>

FILE *fin,*fout;
long p, putere,n;


void citire()
{
  fin=fopen("fact.in","r");
  fout=fopen("fact.out","w");
  fscanf(fin,"%ld",&p);
  fclose(fin);
}



void afisare(long nr)
{
  fprintf(fout,"%ld\n",nr);
  fclose(fout);
}


void calc()
{
  int i;
  i=0; putere=5;
  while (putere<=n)
    {
      putere*=5; i++;
      if (putere<=n) n-=5;
    }
  afisare(n);
}



void main()
{
  citire();
  if (p==0) {fprintf(fout,"1\n");fclose(fout);}
   else if (p>=0)
    {n=p*5;
     calc();
    }
   else {fprintf(fout,"-1\n");fclose(fout);}
}