C :

#include<stdio.h>

int main(){
  int year, month, day;
  scanf("%d%d", &year, &month);
  switch(month){
    case 1:	case 3:	case 5:	case 7:	case 8:	case 10: case 12:
      day = 31;
      break;
    case 4:	case 6:	case 9:	case 11:
      day = 30;
      break;
    case 2:
      if((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0))
        day = 29;
      else
        day = 28;
    break;
  }
  printf("%d", day);
  return 0;
}

C++ :

#include<stdio.h>
int main()
{
int x,y;
scanf("%d %d",&x,&y);
switch(y)
{
case  1: printf("31");break;
case  2: printf("28");break;
case  3: printf("31");break;
case  4: printf("30");break;
case  5: printf("31");break;
case  6: printf("30");break;
case  7: printf("31");break;
case  8: printf("31");break;
case  9: printf("30");break;
case  10: printf("31");break;
case  11: printf("30");break;
case  12: printf("31");break;
}
return 0;
}

Pascal :

program sh;
 var
  a,b:longint;
   begin
    readln(a,b);
 if (a mod 400=0) or (a mod 4=0) and (a mod 100<>0) then
 begin
 if b=1 then writeln('31');
  if b=2 then writeln('29');
    if b=3 then writeln('31');
     if b=4 then writeln('30');
      if b=5 then writeln('31');
       if b=6 then writeln('30');
        if b=7 then writeln('31');
         if b=8 then writeln('31');
          if b=9 then writeln('30');
           if b=10 then writeln('31');
            if b=11 then writeln('30');
             if b=12 then writeln('31');
    end;
    if (a mod 400<>0) and (a mod 4<>0) then
   begin
  if b=1 then writeln('31');
 if b=2 then writeln('28');
   if b=3 then writeln('31');
    if b=4 then writeln('30');
     if b=5 then writeln('31');
      if b=6 then writeln('30');
       if b=7 then writeln('31');
        if b=8 then writeln('31');
         if b=9 then writeln('30');
          if b=10 then writeln('31');
           if b=11 then writeln('30');
            if b=12 then writeln('31');
           end;
end.