Adams remains the President of Sinn FÃ in , with CaoimhghÃ n Ã `` CaolÃ in serving as Sinn FÃ in parliamentary leader in DÃ il Ã ireann , and Martin McGuinness the party 's chief negotiator and effective party head in the Northern Ireland Assembly . Adams remains the President of Sinn FÃ in , with CaoimhghÃ n Ã `` CaolÃ in serving as Sinn FÃ in parliamentary leader in DÃ il Ã ireann , and DaithÃ McKay as head of the Sinn FÃ in group in the Northern Ireland Assembly .