#include<stdio.h>
#include<math.h>
long int n,c,b,a,k,p;
long int h(long int x)
{
 long int y=0;
 while(x)
 {
   y=y+x/5;
   x=x/5;
 }
 return y;
}
long int divide(long int a,long int b)
{
 long int putere;
 //putere = h(c);
 while(a<b)
 {
  c=(a+b)/2;
  putere=h(c);
  if(putere<p) a=c;
  else if(putere>p) b=c;
  else return c;

 }
}
int main()
{

 FILE *in=fopen("fact.in","rt");
 fscanf(in,"%ld",&p);
 fclose(in);
 FILE *out=fopen("fact.out","wt");
 if(p==0) {
  fprintf(out,"1");
  return 0;
 }
 a=0;b=5000000000;
 k=divide(a,b);
 while(k%5) --k;
 if(h(k)==p) fprintf(out,"%ld",k);
 else fprintf(out,"-1");
 fclose(out);
 return 0;
}