#include<fstream.h>
#include<math.h>
ifstream f("fact.in");
ofstream g("fact.out");
long double p,n;
long double zero(long double n)
{long double z=0;
 while(floor(n/5)>0) {z+=floor(n/5); n=floor(n/5);}
 return z;
}
int main()
{f>>p;
 long double z,a=0,b=pow(10,10),c;
 if(p==0) g<<1;
 else{
 while(a<b)
	{c=floor((a+b)/2);
	 z=zero(c);
	 if(z<p) a=c+1;
	 else if(z>p) b=c-1;
		  else a=b=c;
	}

 if(zero(a)==p)
	{while(a/5!=floor(a/5)) a--;
	 g<<a;}
 else g<<-1;
 }

 return 0;
}