#include <fstream>
using namespace std;

inline int count_zero(int x)
{
	int nr=0;
	while (x) {
		nr+=x/5;
		x/=5;
	}
	return nr;
}

int main()
{
	ifstream fIn("fact.in");
	ofstream fOut("fact.out");
	
	int k, li, ls, mij;
	fIn>>k;
	if (!k){ fOut<<1; return 0; }
	
	li=1, ls=k*5;
	while (li<=ls) {
		mij=(li+ls)>>1;
		count_zero(mij)<k ? li=mij+1 : ls=mij-1;
	}
	
	fOut<<(count_zero(li)==k ? li : -1);
	return 0;
}