user: Question: Which slope length has a type of surface lift, and an elevation groundstation smaller than 1974, and a construction year(s) of 1971, and a Name or route of Alpmatten 1?
Columns: ['Name or route', 'type', 'elevation groundstation', 'elevation mountainstation', 'slope length', 'capacity in persons/hour', 'construction year(s)']
Types: ['text', 'text', 'real', 'real', 'real', 'real', 'text']
Sample row: ['Betten Betten Village', 'aerial tramway', 832.0, 1199.0, 872.0, 350.0, '1950 1965']
SQL:

assistant: SELECT "slope length" FROM "Table" WHERE "type" = 'surface lift' AND "elevation groundstation" < 1974.0 AND "construction year(s)" = '1971' AND "Name or route" = 'Alpmatten 1';