#include<fstream>
#include<iostream>
using namespace std;

int main()
{
ifstream f1("fact.in");
ofstream f2("fact.out");
register long n;
f1>>n;

if(n==0){f2<<1;f2.close();return 0;}


register long i, x = 0, nr, j;
for(i=5;;i+=5)
{
	nr = 0;
	j = i;
	while(j)
	{
		if(j%5==0)nr++;
		else break;
		j/=5;
	}
	x += nr;
	if(x>=n)break;
}
f2<<i;
cout<<i;
f1.close();
f2.close();
return 0;}