#include<fstream.h>
int main()
{
 ifstream in("fact.in");
 ofstream out("fact.out");
 long int p,n5=0,i,nr,u;
 in>>p;
 if(p==0) {out<<1;return 0;}
 for(i=5;n5<p;i+=5)
 {

   u=n5;
   n5+=5;
   if(!(i%5))
   {
     nr=i;
     while(!(nr%5)) {nr/=5;n5++;}
   }
   u=u;
 }
 if(n5>p)
 {
   n5=u; i-=5;
   for(;n5<p;i++)
   {
     n5++;
     if(!(i%5))
     {
       nr=i;
       while(!(nr%5)) {nr/=5;n5++;}
     }
   }
 }
 if(n5==p) out<<(i-1)*5;
 else out<<-1;
 return 0;
}