閏年的計算方式：
import java.util.Scanner;

public class Main {

public static void main(String[] args) {
    int y;
    Scanner s=new Scanner(System.in);
    y=s.nextInt();
    if(y>=1990  &&y <= 2050){
        if(y%4==0&&y%100!=0||y%400==0){
            System.out.println("yes");
        }
        else{
            System.out.println("no");
        }
    }else{
        System.out.println("no");
    }


}
 

}