#include <iostream>
#include <fstream>

using namespace std;


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



int main()
{
	unsigned long y,p,t = 0;

	f >> p;

	for ( int x=5 ; ; x +=5 )
	{
		y=x;
		while (y % 5 == 0) {
			t++;
			y = y / 5;
		}

		if ( y == p ) {
			g << x;
			break;
		}
		else if ( y > p ) 
		{ 
			g << -1;
			break;
		}
	}

	return 0;
}