#include <stdio.h>


int main()
{
FILE *f=fopen("fact.in","r"),*g=fopen("fact.out","w");
int p,x=0,n,y;

	fscanf(f,"%d",&p);
	if(p==0)
		{
			fprintf(g,"1");
			return 0;
		}
	n=4*p;
	while(n%5!=0)
       --n;  
	while(x<p)
		{
			x=0;
			y=n;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
   			x+=y/5;	y/=5;
			n+=5;
		}
	if(x==p)
		fprintf(g,"%d",n-5);
	else
		fprintf(g,"-1");
    return 0;


}