Const
    MaxN = 101;
    Inf = 10000;
Var
    Ans : Array [1 .. MaxN, 1 .. MaxN] Of LongInt;
    Inv : Array [Char] Of Char;
    S : String;
    I, J : LongInt;
Function Min(A, B : LongInt) : LongInt;
Begin
    Min := A;
    If A > B Then Min := B;
End;
Function X(L, R : LongInt) : LongInt;
Var
    Best, J : LongInt;
Begin
    If L > R Then
    Begin
        X := 0;
        Exit;
    End;
    If L = R Then
    Begin
        X := 1;
        Exit;
    End;
    If Ans[L, R] <> Inf Then
    Begin
        X := Ans[L, R];
        Exit;
    End;
    Best := Inf;
    If Inv[S[L]] = S[R]
    Then Best := X(L + 1, R - 1);
    For J := L To R - 1 Do
        Best := Min(Best, X(L, J) + X(J + 1, R));
    Ans[L, R] := Best;
    X := Best;
End;
Begin
    Inv['('] := ')';
    Inv['['] := ']';
    Inv['{'] := '}';
    For I := 1 To MaxN Do
        For J := 1 To MaxN Do
            Ans[I, J] := Inf;
    ReadLn(S);
    WriteLn(X(1, Length(S)));
End.