Program fact;
var f, g:text;
    i, j, n, k:byte;
    p:longint;
    m:extended;
begin
assign(f, 'fact.in');
assign(g, 'fact.out');
reset(f); rewrite(g);
readln(f, n);
if n=0 then begin writeln(1);
                  inc(k);
            end;
p:=1; m:=1; k:=0;
if k=0 then begin
For i:=1 to n do p:=p*10;
For i:=5 to 170 do begin For j:=1 to i do m:=m*j;
                         if frac(m/p)=0 then begin writeln(g, i);
                                                   inc(k);
                                                   break;
                                             end;
                         m:=1;
                   end;
             end;
if k=2 then write(g, -1);
close(f); close(g);
end.