program codez;
type
    a=array[1..10000] of string;
    b=array[1..10000] of integer;
var
    f1,f2:text;
    n,i,j,k,t,w,ww,ans:longint;
    flag1,flag2,flag3:boolean;
    ls:string;
    s:a;
    num:b;
begin
   assign(f1,'codez.in');
   assign(f2,'codez.out');
   reset(f1);rewrite(f2);
   readln(f1,n);
   for i:=1 to n do
   readln(f1,s[i]);
      for i:=1 to 10000 do
          num[i]:=1; 
          t:=1;w:=n;
          ans:=500;
          flag1:=true;flag3:=false;
       while flag1 do begin ww:=w;
                     for i:=1 to n do
                     for j:=t to w do
                      begin ls:=s[j]+s[i];
                            flag2:=true;
                            for k:=1 to w do
                            if ls=s[k] then begin inc(num[k]);
                               if (num[k]>2)and(length(s[k])<=ans)
                                  then begin ans:=length(s[k]);
                                  flag3:=true;end;
                                  flag2:=false;
                               break;
                                      end;
                            if flag2 then 
                      begin inc(ww);
                           s[ww]:=ls;end;
                      end;
                  t:=w+1;w:=ww;
             if (w>=10000)or(t>=w) then 
             flag1:=false;
               end;
if flag3 then writeln(f2,ans)
         else writeln(f2,'-1');
close(f1);close(f2);
end.