user: Question: Can you tell me the sum of Swing to gain that has Constituency of Caithness, Sutherland and Easter Ross?
Columns: ['Rank', 'Constituency', 'Winning party 2003', 'Swing to gain', "Labour's place 2003", 'Result']
Types: ['real', 'text', 'text', 'real', 'text', 'text']
Sample row: [1.0, 'Dundee East', 'SNP', 0.17, '2nd', 'SNP hold']
SQL:

assistant: SELECT SUM("Swing to gain") FROM "Table" WHERE "Constituency" = 'Caithness, Sutherland and Easter Ross';