#include<fstream>
using namespace std;
int main()
{
	ifstream fin("fact.in");
	ofstream fout("fact.out");
	int p;
	fin >> p;
	int r = 0;
	if (p==0)
		fout << 1;
	else
	{
		int y = 5;
		int n = 5;
		while (r<p-1)
		{
			int i = y;
			while (i%5==0)
			{
				r = r+1;
				i = i/5;
			}
			y = y+5;
			n = n+5;
		}
		fout<<n;
	}
fin.close();
fout.close();
}