#include<fstream.h>
#include<math.h>
int main()
{
	 int p,n,c,m,put,i,j;
	 ifstream f("fact.in");
	 ofstream g("fact.out");
	 f>>p; n=1;
	 
	 if(p==5)n=-1;
     else
	 { 
		 i=1; j=1000000000;
		 while(i<j){
			 
		 m=(i+j)/2;
		 c=m; put=0;
		 while(c){ put+=c/5;
		            c/=5;
		          }
		 if(put<p)i=m+1;
		 else if(put>p)j=m-1;
			  if(put==p){n=m;break;}      		 
           }
		 if(i>j)n=-1;}
	 g<<n;
	 f.close();
	 g.close();
	 return 0;
}