#include<fstream>
using namespace std;
int zero(int x)
{
	int putere=1;
	int z=0;
	while(x>=putere)
	{
		putere=putere*5;
		z=z+x/putere;
	}
	return z;
}
ifstream f("fact.in");
ofstream g("fact.out");
int i,p;
int main()
{
	f>>p;
	for(i=1; ;i++)
	{
		if(zero(i)==p)
		{
			g<<i;
			break;
		}
		if(zero(i)>p){g<<"-1";break;}
	}
		return 0;
}