#include <fstream>
using namespace std;
int P, Factorial;
ifstream cin ("fact.in");
ofstream cout ("fact.out");
int calculateFact(int &P)
{
    int Fac = 10 * (P / 2);
    if(P % 2 == 1)
        Fac += 5;
    return Fac;
}
int main()
{
    cin>>P;
    Factorial = (!P) ? 1 : calculateFact(P);
    cout<<Factorial;
    cin.close();
    cout.close();
    return 0;
}