#include <fstream.h>

ifstream f("fact.in");
ofstream g("fact.out");

long p;

int main()
{
    long a,b,c;
     f>>p;
     if (p==0)
       g<<1;
     else
     {
       a=5;
       b=p*10;
       c=(a+b)/2;
       int sw=0;
       long x;
       long j,i;
       while (a<=b && sw==0)
       {
           
             x=0;
             for (j=5;j<=c;j=j+5)
              {
                i=j;
                while (i%5==0)
                  {
                      x++;
                      i=i/5;
                  }
              }
             if (p==x)
               {
               sw=1;
               while (c%5!=0)
                 c--;
               g<<c;  
               
               }
             else
               if (p<x)
                 b=c-1;
               else
                 a=c+1;
             c=(a+b)/2;
             
       }
       if (sw==0)
         g<<"-1";
     }
       f.close();
       g.close();      
}