#include<fstream>
using namespace std;
	fstream fin("fact.in",ios::in),fout("fact.out",ios::out);

int main()
{
	int p,ok,t,i,j,a=1,v2=0,v5=0;
	fin>>p;
	ok=1;
	while(ok)
	{
		
		i=a;
		j=a;
		
		t=0;
		while(i%2==0)
		{
			t++;
			i/=2;
		}
	//	fout<<t<<" "<<i<<" ";
	
			v2+=t;
		
		t=0;
		while(j%5==0)
		{
			t++;
			j/=5;
		}

			v5+=t;
		if(v5>=p&&v2>=p)
			ok=0;
		a++;
	}
	fout<<a-1;

fin.close();
fout.close();
return 0;
}