#include<fstream>
#include<limits.h>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int main(){
	int n,p,gasit,c,i,m,j,cm;
	in>>p;
	j=1000000000;//LONG_LONG_MAX;
	i=p+1;
	gasit=0;
	while(i<=j && !gasit){
		m=(i+j)/2;
		c=0;
		cm=m;
		while(m){
			c+=m/5;
			m/=5;
		}
		if(c==p)
			gasit=1;
		else
			if(p>c)
				i=cm+1;
			else
				j=cm-1;
	}
	if(gasit)
		cm=cm/5*5;
	if(cm==0)
		cm=1;
	if(!gasit)
		cm=-1;
	out<<cm;
	return 0;
}