#include<iostream>
#include<fstream>
using namespace std;
int main()
{long n=1,p,k,i=0,uc,cn,l=1,uc1;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;

while(l==1)
{i++;
k=0;
n=n*i;
cn=n;
uc1=cn%10;
if (cn%10==0)
	while (cn!=0) 
	{
		uc=cn%10;
		
	cn=cn/10;
	if(uc==0&&uc1==0) k++;
	uc1=uc;}
if (k==p) l=0;
}
g<<i;

f.close(); g.close();
return 0;
}