How many ships for the nation with grand total of 20?
CREATE TABLE "naval_forces_operation_mainbrace_1952_ci" (
  "nato_member" text,
  "aircraft_carriers" text,
  "battleships" text,
  "cruisers" text,
  "escorts" text,
  "submarines" text,
  "torpedo_boat_squadrons" text,
  "s_motor_ship_s_naval_trawler" text,
  "grand_total" real
);
SELECT "s_motor_ship_s_naval_trawler" FROM "naval_forces_operation_mainbrace_1952_ci" WHERE "grand_total"=20;