#include <iostream>
#include <fstream>
using namespace std;

int main(){
	fstream fin("fact.in",ios::in);
	fstream fout("fact.out",ios::out);
	unsigned hp=0,p,k,r=-1;
	fin>>p;
	if(p!=0){
		for(int i=5;hp<p;i+=5){
			unsigned c=0;
			k=i;
			while(k%5==0){
				c++;k/=5;
			}
			hp+=c;
			if(hp==p){
				r=i;
			}
		}
		fout<<r;
	}else{
		fout<<-1;
	}
fin.close();
fout.close();
}