CREATE TABLE table_204_312 (id DECIMAL, "stage" TEXT, "date" TEXT, "route" TEXT, "terrain" TEXT, "length" TEXT, "winner" TEXT)

how many number of stages in the tour de france contain stages with mountains ?
SELECT COUNT("stage") FROM table_204_312 WHERE "terrain" = 'stage with mountain(s)'
SELECT COUNT("stage") FROM "table_204_312" WHERE "terrain" = 'stage with mountain(s)'