#include<fstream.h>
#define input "fact.in"
#define output "fact.out"


int check(int x,int p)
	{
	long z,ok;
	z=5;
	ok=0;
	while(z<=x)
		{
		ok+=x/z;
		z=z*5;
		}
	if(p==ok)
		return 1;
	else
		return 0;
	}
int main()
	{
	long long h,x,p;
	int gr;
	ifstream fin(input);
	ofstream fout(output);
	fin>>p;
	x=p;
	h=1;
	gr=1;
	if(x>=1)
		{
		while(h*5+1<x)
			{
			h=(h*5)+1;
			gr++;
			}
		while(h!=1)
			{
			x-=(x/h);
			h--;
			h=h/5;
			}
		x=x*5;
		if(check(x,p))
			fout<<x;
		else
			fout<<"-1";
		}
	else
		if(p==0)
			fout<<"1";

	fout.close();
	fin.close();
	return 0;
	}