Find the Number of Days in a Month Using switch

#include <stdio.h>

int main(void)
{
    int month, year, days;
    printf("Enter month number and year: ");
    scanf("%d %d", &month, &year);
    switch (month) {
        case 1: case 3: case 5: case 7: case 8: case 10: case 12:
            days = 31; break;
        case 4: case 6: case 9: case 11:
            days = 30; break;
        case 2:
            days = (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) ? 29 : 28;
            break;
        default: puts("Invalid month number."); return 0;
    }
    printf("Days = %d\n", days);
    return 0;
}