CREATE TABLE table_203_778 (id DECIMAL, "representative" TEXT, "title" TEXT, "presentation\ of credentials" TEXT, "termination\ of mission" TEXT, "appointed by" TEXT)

who became the ambassador after the completion of hewson ryan 's mission ?
SELECT "representative" FROM table_203_778 WHERE "presentation\nof credentials" > (SELECT "presentation\nof credentials" FROM table_203_778 WHERE "representative" = 'hewson a. ryan') ORDER BY "presentation\nof credentials" LIMIT 1
SELECT "representative" FROM "table_203_778" WHERE "presentation\nof credentials" > (SELECT "presentation\nof credentials" FROM "table_203_778" WHERE "representative" = 'hewson a. ryan') ORDER BY "presentation\nof credentials" NULLS FIRST LIMIT 1