{
 haoi2009 moni1 t1 codez
 rp++
 time:2009.4.21
}
program cch(input,output);
var
 i,n,max:longint;
 s:array[1..50] of string;
begin
 assign(input,'codez.in');
 assign(output,'codez.out');
 reset(input);
 rewrite(output);
 readln(n);
 for i:=1 to n do readln(s[i]);
 if (n=1)or(n=2) then writeln(-1)
  else
   begin
    max:=0;
    for i:=1 to n do
     if length(s[i])>max then max:=length(s[i]);
    writeln(max);
   end;
 close(input);
 close(output);
end.