#include<fstream>
using namespace std;
int main()
{	int p,n,a,b;
	ifstream in("fact.in");
	ofstream out("fact.out");
	in>>n;
	if(n==0) out<<1<<"\n";
	     else if(n%2==0)
				{
					a=n/2;
					a*=10;
					out<<a<<"\n";
				}	
			else if (n/2==1) //out<<((n/2)*10)-5<<"\n";
				{
					b=n/2;
					b*=10;
					b-=5;
					out<<b<<"\n";
				}	
				
	/*in.close;
    out.close;
	*/return 0;
}