C语言，输入年和月份，输出该年该月份的天数。

#include <stdio.h>

int main() {
    int year, month;
    printf("请输入年份和月份：");
    scanf("%d%d", &year, &month);
    int days = 0;
    if (month == 2) {
        if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
            days = 29;
        } else {
            days = 28;
        }
    } else if (month == 4 || month == 6 || month == 9 || month == 11) {
        days = 30;
    } else {
        days = 31;
    }
    printf("%d年%d月有%d天\n", year, month, days);
    return 0;
}