#include<stdio.h>
int main()
{
    int month,year,days,weak;
    printf("Please input year:\n");
    scanf("%d",&year);
    printf("Please input month:\n");
    scanf("%d",&month);
    days=CheckMonth(month,year);
    weak=CheckWeak(month,year);
    printf("\n");
    CalendarPrinter(weak,days);
    return 0;
}
int CalendarPrinter(int a,int b)//给出1号是星期几和当前月的天数
{
    int times=0,day=1,weak=1,x=1;
    if(b!=28)
        if(a==6&&b==30)
        times=5;
        else
        times=6;
    else if(a!=1)
            times=5;
         else
            times=4;
    //printf("%d",times);
    //确定有多少周
    printf(" Mon Tue Wed Thu Fri Sat Sun\n");
    for(weak=1;weak<=times;weak++)
    {
        for(x=1;x<=7;x++)
        {
            if(weak==1&&x<a)
                printf("    ");
            else
            {
                printf("%4d",day);
                if(day==b)
                    return 0;
                day++;
            }
        }
        printf("\n");
    }

    return 0;
}
int CheckLeap(int year)//输入年份，闰年返回1，平年返回0
{
    if(year%4==0&&year%100!=0||year%400==0)
        return 1;
    else
        return 0;
}
int CheckMonth(int month,int year)//输入月份和年份，返回当月天数，失败返回0
{
    int day;
    switch(month){
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:day=31;break;//以上全部是大月
        case 4:
        case 6:
        case 9:
        case 11:day=30;break;//以上全部是小月
        case 2:{
        if(CheckLeap(year)==1)
            day=29;
        else
            day=28;
        break;
        }
        default:day=0;break;//返回错误代码：0
    }
    return day;
}
int CheckWeak(int month,int year)//输入月份和年份，返回当月1日是星期几
{
    int k=0,a,b,h=0;
    if(year%100!=0&&year%4==0||year%400==0)
    {
        switch(month)//闰年
        {
            case 12:k=k+30;
            case 11:k=k+31;
            case 10:k=k+30;
            case 9:k=k+31;
            case 8:k=k+31;
            case 7:k=k+30;
            case 6:k=k+31;
            case 5:k=k+30;
            case 4:k=k+31;
            case 3:k=k+29;
            case 2:k=k+31;
        }
    }
    else
    {
        switch(month)//平年
        {
            case 12:k=k+30;
            case 11:k=k+31;
            case 10:k=k+30;
            case 9:k=k+31;
            case 8:k=k+31;
            case 7:k=k+30;
            case 6:k=k+31;
            case 5:k=k+30;
            case 4:k=k+31;
            case 3:k=k+29;
            case 2:k=k+31;
        }
    }
    a=k+1;
    for(b=1900;b<year;b++)
    {
        if(b%100!=0&&b%4==0||b%400==0)//闰年
            h=h+366;
        else//平年
            h=h+365;
    }
    if((a+h-1)%7==0)
        return 7;
    else
        return (a+h-1)%7;
}