Program LastChance;

var n,p,k,x,m,r:longint;

    i,o:text;

begin
    assign(i,'fact.in');
    assign(o,'fact.out');
    reset(i);
    rewrite(o);
    Read(i,p);
    k:=0;n:=1;
    While (k<>p) and (k<=100000000) do begin
                                         inc(n);

                                         if (n>=5) and (n mod 5=0) then begin
                                                                     x:=n;r:=0;m:=1;
                                                                    while x>=5 do begin
                                                                                  x:=x div 5;
                                                                                  inc(r);
                                                                                  end;
                                                                    k:=k+r;
                                                                        end;
                                         end;
     if (k=p) and (k<=100000000) then write(o,n)
                                 else write(o,-1);
    close(i);
    close(o);
end.