#include<fstream>
using namespace std;
long long nrzero(int x)
{
    int l,v=0,s=0;
    l=x;
    while(l>0)
    {
        v=v+l/5;
        l=l/5;
    }
    while(x>0)
    {
       s=s+x/2;
       x=x/2;
    }
    if(s>=v)
        return v;
    else
        return s;
}
int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    int p,r=1;
    in>>p;
    while(nrzero(r)<p)
        r++;

        if(nrzero(r)==p)
            out<<r;
        else
            out<<-1;
}