#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    long long P,p=1,copieP;
    unsigned int i=1,contor=0;
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin >> P;
    copieP=P;
    if (P==0)
    {
        fout << 1;
    }
    else
    {
        while (copieP%10==0)
        {
            ++contor;
            copieP=copieP/10;
        }
    fout << P*5-contor*5;
    }
    return 0;
}