#include <fstream>

using namespace std;

int putere(int x)
{
    int i=0;
    while(!x)
    {
        i++;
        x/=2;
    }
    return i;
}
int main()
{
    int p;
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>p;
    if(!(p%5))
        fout<<(p-putere(p/5) )*5;
    else
        fout<<p*5;
    return 0;
}