#include <stdio.h>

int main() {
    int month, year, i, j, days, first_day;

    printf("Enter the month (1-12): ");
    scanf("%d", &month);
    printf("Enter the year: ");
    scanf("%d", &year);

    // Determine number of days in the month
    switch (month) {
        case 2:
            if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
                days = 29;
            } else {
                days = 28;
            }
            break;
        case 4: case 6: case 9: case 11:
            days = 30;
            break;
        default:
            days = 31;
    }

    // Determine the first day of the month
    // January and February are treated as months 13 and 14 of the previous year
    if (month == 1 || month == 2) {
        month += 12;
        year--;
    }
    first_day = (1 + (13 * (month + 1)) / 5 + year + (year / 4) - (year / 100) + (year / 400)) % 7;

    // Print the calendar
    printf("Sun Mon Tue Wed Thu Fri Sat\n");
    for (i = 0; i < first_day; i++) {
        printf("    ");
    }
    for (i = 1; i <= days; i++) {
        printf("%3d ", i);
        if ((first_day + i) % 7 == 0) {
            printf("\n");
        }
    }
    return 0;
}