编写程序，计算贷款的月支付额公式

package Chapter_2;
import java.util.Scanner;
public class lianxi2_7 {
   public static void main(String args[]) {
     // TODO Auto-generated method stub
     double a,b,c;
     Scanner input=new Scanner(System.in);
     System.out.println("请输入贷款的年利率：");
     a=input.nextDouble();
     System.out.println("请输入贷款总额：");
     b=input.nextDouble();
     System.out.println("请选择贷款年数：");
     c=input.nextDouble();
     double montha=a/12;
     double pmt=(b*montha)/(1-1/Math.pow(1+montha, c*12));
     System.err.println("月支付额为:"+pmt);
   }
}