int sum = 0;
     int mo = month-1;
        for(;mo > 0 ;mo--)
        {
            switch(mo)
            {
                case 1:
                       sum += 31;
                       break;
                case 2:
                       if((year % 4 == 0 && year % 100 != 0) || year & 400 == 0)
                       sum += 29;
                       else sum += 28;
                       break;
                case 3:
                       sum += 31;
                       break;
                case 4:
                       sum += 30;
                       break;
                case 5:
                       sum += 31;
                       break;
                case 6:
                       sum += 30;
                       break;
                case 7:
                       sum += 31;
                       break;
                case 8:
                       sum += 31;
                       break;
                case 9:
                       sum += 31;
                       break;
                case 10:
                       sum += 31;
                       break;
                case 11:
                       sum += 31;
                       break;
                case 12:
                       sum += 31;
                       break;
            }
        }
        sum += day;
        printf("%d年%d月%d日是该年的第%d天",year,month,day,sum);