#include <fstream>
using namespace std;

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

int cauta(int p)
{
    // li = limita inferioara
    // ls = limita superioara
	int li=1,ls=500000000,mij,cinci,count=0,rez=-1;
	while(li<=ls)
	{
		count=0;
		mij=(li+ls)/2;
		for(cinci=5;cinci<=mij;cinci*=5)
		{
			count+=mij/cinci;
		}

		if(count==p) { rez=mij; ls=mij-1;}
		if(count<p) li=mij+1;
		if(count>p) ls=mij-1;

	}
	return rez;
}

int main()
{
	int n;
	f>>n;
    g<<cauta(n)<<endl;
	return 0;
}