C++ :

#include<bits/stdc++.h>
using namespace std;
int main() {
	int n,y;
	cin>>n>>y;
	if(y==1||y==3||y==5||y==7||y==8||y==10||y==12){
		cout<<31<<endl;
	}else if(y==4||y==6||y==9||y==11){
		cout<<30<<endl;
	}else if(y==2){
		if(n%4==0&&n%100!=0){
			cout<<29<<endl;
		}else if(n%400==0){
			cout<<29<<endl;
		}else{
			cout<<28<<endl;
		}
	}
	return 0;
}

Java :

import java.util.Scanner;
public class Main{

public static void main (String[] args){
	Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		if(b ==1 || b == 3 || b == 5 || b == 7 || b ==8 || b ==10 || b ==12) {
			System.out.println(31);
		}
		if(b==4 ||b==6||b== 9||b == 11) {
			System.out.println(30);
		}
		if(b == 2) {
				if(a % 4 == 0 && a % 100 != 0 || a % 400 == 0) {
				System.out.println(29);
			} else{
				System.out.println(28);
			}
		
		}
		}
		
}

Python :

year,month=map(int,input().split())
if month in (1,3,5,7,8,10,12):
    day=31
    print(day)
elif month in (4,6,9,11):
    day=30
    print(day)
elif month==2:
    if year%400==0 or(year%4==0 and year%100!=0):
        day=29
        print(day)
    else:
        day=28
        print(day)