program bing;
type
 zc=array[0..5000] of char;
var
 f1,f2:text;
 n:longint;
 s:zc;
 m,min,i:longint;
procedure init;
var
 i,j:longint;
begin
 assign(f1,'palin.in');reset(f1);
 assign(f2,'palin.out');rewrite(F2);
 readln(f1,n);
 for i:=1 to n do read(f1,s[i]);
 min:=10000;
end;
procedure nb(x,y:longint);
var
 i,j:longint;
begin
 i:=x;j:=y;m:=0;
 repeat
 while (s[i]=s[j])and(i>0) do begin dec(i);inc(j);end;
 if i=0 then
 begin m:=m+n-j+1;
 if m<min then min:=m;end
 else inc(m,2);
 dec(i);inc(j);
 until i<0;
end;
begin
 init;
 for i:=1 to n do
 begin
 nb(i,i);
 if s[i]=s[i+1] then nb(i,i+1);
 end;
 write(f2,min);
 close(f1);close(F2);
end.