What is the minimum stage where Sergei Smetanine won?
CREATE TABLE "jersey_progress" (
  "stage" real,
  "winner" text,
  "general_classification" text,
  "points_classification" text,
  "mountains_classification" text,
  "combination_classification" text,
  "team_classification" text
);
SELECT MIN("stage") FROM "jersey_progress" WHERE "winner"='Sergei Smetanine';