What is the length of retirement for president Sharma, Shankar Shankar Dayal Sharma?
CREATE TABLE "list" (
  "president" text,
  "date_of_birth" text,
  "date_of_inauguration" text,
  "age_at_inauguration" text,
  "end_of_term" text,
  "length_of_retirement" text,
  "date_of_death" text,
  "lifespan" text
);
SELECT "length_of_retirement" FROM "list" WHERE "president"='sharma, shankar shankar dayal sharma';