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



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