编写程序计算了整数2-20中所有整数的不含有1的因子数量，并将因子数量为奇数的整数输出出来。

#include<stdio.h>

int get_days_of_month(int year, int month)
{//补足函数
 
	int days,flag;                 
	//printf("Please input year:");   //         
	//scanf("%d",&year);//                      
	//printf("Please input month:"); //           
	//scanf("%d",&month);//


	if(year%400==0)                                  
		flag=1;         //flag为1表示是闰年
	else                                     
	{ if(year%4==0&&year%100!=0)   flag=1;
		else  flag=0;      //flag为0表示非闰年
	}

	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:{ if(flag==1)  days=29;       
			else days=28; } break;
	default: printf("month input error\n");  
	}

	//printf("%d年%d月份有%d天\n",year,month,days);//
	return  days;
}

int main(void)
{
    int year, month, day;
    int m;
    int sum;

    sum = 0;
    scanf("%d %d %d", &year, &month, &day);
    for (m = 1; m <month; ++m) 
		{
			int days_of_month, flag;
			//第二步：判断当前第m月份天数
			//将当前第m月份天数赋值给days_of_month
			days_of_month=get_days_of_month(year, m);
			//用sum把每月的时间累加起来
			sum += days_of_month;
		}
	//第三步：循环后，加上当月的日期
	sum += day;
    printf("%d\n", sum);
	return 0;
}