#include <fstream>
using namespace std;

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

long long nrzero(long long x){
	long long s=0;long long put=5;
	while(x/put>0){
		s=s+x/put;
		put*=5;
	}
	return s;
}


long long int p,mj,dr=100000000000000ll,st=2,i,logic,n;

int main(){
	f>>p;
	if(p==0)
		g<<1;
	
		else{

					while((logic!=1)&&(st<=dr)){
		
				mj=(st+dr)/2;
			if(nrzero(mj)==p){
			logic=1;
			n=mj;
		}
			else if(p<nrzero(mj))
				dr=mj-1;
			else if(p>nrzero(mj))
					st=mj+1;
	}
	n=n-n%5;
	if(logic==0)
	g<<-1;
	else
	g<<n;
		}
	return 0;
}