program magneti;
Uses Math;
const
    MAXN = 100000;
var
    N,i,h           : longint;
    descrizione, mag : array[0..MAXN] of char;
 
 
 
function gira(x: longint; var m: array of char): longint;
var j,conta:longint;
begin
    j:=3;
    while j<x-1 do if m[j]=m[1] then begin conta:=conta+1; j:=j+2; end;
    gira := min(x div 2 - conta, conta);
end;
begin
    readln(N); h:=1;
    for i:=1 to N do begin read(descrizione[i]); if (descrizione[i]<>'(') and (descrizione[i]<>')') then begin mag[h]:=descrizione[i]; h:=h+1; end; end;  readln;
    for i:=1 to h do write(mag[i]); 
    writeln(gira(h, mag));
end.
 
 

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