#include <fstream>
using namespace std;
ifstream fin("file.in");
ofstream fout("file.out");
int num0Fin(int num)
{
    if (num % 10)
        return 0;
    return 1 + num0Fin(num / 10);
}
int main ()
{
    int put , num = 1 , val = 1;
    fin >> put;
    while (num0Fin(num) != put)
        num *= val++;
    fout << val - 1;
    return 0;
}