#include<fstream>
using namespace std;
unsigned long long int mij,li,lf=40000010,p;
unsigned int ok=0;
ifstream f("fact.in");
ofstream g("fact.out");
unsigned long int nz(unsigned long int n){
	unsigned int nrd=0,d,aux;
	for(d=1;d<=n;++d)
		if(d%5==0){
			aux=d;
			while(aux%5==0){
				++nrd;
				aux/=5;
			}
		}
	return nrd;
}
int main(){
	f>>p;
	while(li<lf && ok==0){
		mij=(li+lf)/2;
		if(nz(mij)==p)
			ok=1;
		else
			if(nz(mij)<p)
				li=mij+1;
			else
				lf=mij-1;
	}
	if(ok==0)
		g<<-1;
	else{
		while(nz(mij)==p)
			--mij;
		g<<mij;
	}
	return 0;
}