Can you tell me the sum of Swing to gain that has Constituency of caithness, sutherland and easter ross?
CREATE TABLE "labour_targets" (
  "rank" real,
  "constituency" text,
  "winning_party_2003" text,
  "swing_to_gain" real,
  "labour_s_place_2003" text,
  "result" text
);
SELECT SUM("swing_to_gain") FROM "labour_targets" WHERE "constituency"='caithness, sutherland and easter ross';