How many years was the operating profit (s$m) 717.1?
CREATE TABLE "singapore_airlines_group_financial_highl" (
  "year_ended" text,
  "revenue_s_m" text,
  "expenditure_s_m" text,
  "operating_profit_s_m" text,
  "profit_before_taxation_s_m" text,
  "profit_attributable_to_equity_holders_s_m" text,
  "eps_after_tax_diluted_cents" text
);
SELECT COUNT("profit_before_taxation_s_m") FROM "singapore_airlines_group_financial_highl" WHERE "operating_profit_s_m"='717.1';