Cast on 112 sts and work ribbing in the round.
When the hat measures 28 cm, begin decreases: p2tog the purls, k2tog the knits. Switch to the double-pointed needles.
Work p1 k1 ribbing for 2 cm. On the next round, k2tog to end. Knit 1 round even, then k2tog to end of round. Break yarn and pass it through the remaining sts.
Fold the brim once or twice.