#include<stdlib.h>
#include<stdio.h>
#include<fstream>


using namespace std;


long long fact(long p){
	long s=0, nr0=1, nr=10, i=5;
	if(p==0) return 1;
	while(s<=p){
		
		if(i==nr*10){
			nr=nr*10;
			nr0++;
		}
		if(i%10==0) s=s+nr0;
		else {
		   long n=i;
		   while(n%5==0){
		   	  s=s+1;
		   	  n=n/5;
		   } 		
		}
		if(s==p) return i;
		i=i+5;
	}
	return -1;
}




int main(){
ifstream in; ofstream out;
in.open("fact.in"); out.open("fact.out");
out.clear();

long p;
in>>p; 

out<<fact(p);
	
return 0;	
}