#include <stdio.h>
FILE *f,*g;
long long p,s,i,j,r,k;
int main()
{
   FILE *f=fopen("fact.in","rt");
   FILE *g=fopen("fact.out","wt");
   fscanf(f,"%lld",&p);
   j=p-p/5-1;
   s=0;
   k=0;
   while (s!=p&&j<p&&k<100000)
     {
       k++;
       j++;
       s=0;
       i=j;
       while (i>0)
         {
           s+=i;
           i/=5;
         }
     }
   if (p==0)
     fprintf(g,"1\n");
    else
     if (s==p)
       fprintf(g,"%lld\n",j*5);
      else
       fprintf(g,"-1\n");
   fclose(f);
   fclose(g);
   return 0;
}