#include <fstream>
using namespace std;

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

int main()
{
	int p;
	fin >> p;
	int n = 1;
	int nr0 = 0;
	int i = 1;
	if ( nr0 == p )
		fout << 1;
	else
	{
		while ( nr0 != p )
		{
			n++;
			i *= n;
			if ( i >= 60 && i % 10 == 0 )
			{
				nr0 ++;
				i /= 10;
			}
		}
		fout << n;
	}
	fout.close();
	fin.close();
	return 0;
}