#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int luis(int gogu)
{
    int nr0=0;
    while(gogu>=5)
    {
        nr0+=gogu/5;
        gogu/=5;
    }
    return nr0;
}
int pas=1<<20;
int main()
{
    int gogu;
    in>>gogu;
    int r=0;
    int pas=1<<29;
    while(pas!=0)
    {
        if(luis(r+pas)<gogu)
            r+=pas;
        pas/=2;
    }
    r++;
    if(luis(r)==gogu)
        out<<r;
    else
        out<<-1;
    return 0;
}