C++ :

#include<iostream>
using namespace std;
int main()
{
	int year,month;
	cin>>year>>month;
	switch(month)
	{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:cout<<31<<endl;break;
		case 4:
		case 6:
		case 9:
		case 11:cout<<30<<endl;break;
		case 2: if((year%4==0 && year%100!=0) || year%400==0) 
		{
			cout<<29<<endl;break;
		}
		else
		{
			cout<<28<<endl;break;
		} 
	}
	return 0;
}

Pascal :

var month,year:integer;b:boolean;
begin
  readln(year,month);
  b:=false;
  if (year mod 4=0)and(year mod 100<>0)or(year mod 400=0) then b:=true;
  case month of
    1,3,5,7,8,10,12:writeln(31);
	4,6,9,11:writeln(30);
	2:if b then writeln(29)else writeln(28);
  end;
end.