#include<fstream>
#define i64 unsigned long long 
using namespace std;
ifstream f("fact.in"); ofstream g("fact.out");
i64 d61, st, dr, m, c[100];
int i, p, nr;
inline int fct(int n)
{
	int s=0, i=1;
	while(c[i]<=n) s+=n/c[i++];
	return s;
}
int main()
{	d61=1LL<<61;
    c[0]=1; 
	while(4*c[i]<d61-c[i]){i++; c[i]=c[i-1]*5;}
	f>>p; st=1; dr=p*5; int w=1;
	while((st<=dr) && w)
	   {m=(st+dr)/2;
	    nr=fct(m);
		if(nr==p) {g<<m-m%5<<"\n"; w=0;}
			else if(nr<p) st=m+1; else dr=m-1;
	   }
	if(w) g<<"-1\n";
	return 0;
}