#include <stdio.h>
 
int days_in_month(int month, int year) {
    if ( month > 12 || month < 1 ) return 0;
 
    if (month == 4 || month == 6 || month == 9 || month == 11) return 30;
    else if (month == 2) return (((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) ? 29 : 28);
    return 31;
}
 
int main() {
    printf("10 - 2017 : %d\n", days_in_month(10, 2017));	
    printf("2  - 2000 : %d\n", days_in_month(2, 2000));
    printf("2  - 1300 : %d\n", days_in_month(2, 1300)); // Does not work !
    printf("2  - 2018 : %d\n", days_in_month(2, 2018));
    printf("2  - 2016 : %d\n", days_in_month(2, 2016));
}

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