#include<fstream>
#define MAXN 20000000

using namespace std;

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

unsigned short v[MAXN];

int main()
{
	int n,nr=0;
	in>>n;
	if(n==0)
	{
		out<<"1";
		return 0;
	}
	for(int i=5;nr<n;i+=5)
	{
		if(i%25==0)
		{
			v[i/5]=v[i/25]+1;
		}
		else
			v[i/5]++;
		nr=nr+v[i/5];
			if(nr==n)
			{
				out<<i;
				return 0;
			}			
	}
	if(nr>n)
		out<<"-1";
	return 0;
}