var n,p,i,s:longint;
    f,g:text;
    nr2,nr5:integer;
    ok:boolean;
procedure nr(x:longint;var nr2,nr5:integer);
begin
while (x mod 2 = 0)and (x>0) do begin inc(nr2); x := x div 2; end;
while (x mod 5 = 0) and (x>0) do begin inc(nr5); x:= x div 5; end;
end;

begin
assign(f,'fact.in'); reset(f);
assign(g,'fact.out'); rewrite(g);
readln(f,n);
i:=1;                  ok := false;
while (nr2 <n) and (nr5<n) do begin
                   nr(i,nr2,nr5);
                   if (nr2=nr5)and(nr2=n) or (nr2>nr5) and (nr5=n) or (nr5>nr2) and (nr2=n) then
                   begin
                   writeln(g,i); ok:=true;
                   break;
                   end;
                   inc(i);
                              end;
if n=0 then writeln(g,'1') else
if not ok then writeln(g,'-1');



close(f); close(g);
end.