what would the output of this code be?

Question

int startDay = 6;
int day = 22;
switch(startDay)
{
case 5: day += 1;
case 6: day = day + 1;
case 0: ++day;
case 1: day++;
case 2: day += 1;
default: day = day + 1;

}
printf("day: %d\n", day);

the answer is 27, but i thought it would just do case 6, so day +1 so 23