C++ :

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