#include<fstream.h>

int p;

int zero(int n)
{
	int k=0;
	while(n)
	{
		k=k+n/5;
		n=n/5;
	}
	return k;
}

int main()
{
	ifstream f("fact.in");ofstream g("fact.out");
	int n=0,z=0;
	f>>p;
	if(p==0)g<<1;
	else
	{
		while(z<p){n=n+5;z=zero(n);}
		if(z==p)g<<n;
		else g<<-1;
	}
	f.close();g.close();
	return 0;
}