求大虾帮忙，新手求教，实在不知道为啥错了

红色字体处是编译时的报错
#include <cstdlib>
#include <iostream>

using namespace std;

class Box
{
      public:
             Box(int h=10,int w=12,int len=15):height(h),width(w),length(len){}     //声明有默认参数的构造函数，用参数初始化表对成员初始化
             Box(int l=10,int s=10):lng(l),shrt(s){}
             int volume();
             int square();
      private:
              int height;
              int width;
              int length;
              int lng;
              int shrt;        
      };
int Box::volume()
{
    return(height*width*length);
    }
int Box::square()
{
    return(lng*shrt);
    }   
           
int main(int argc, char *argv[])
{
    Box a[3]=                                   //定义对象数组
    {
        Box(10,12,15),                          //调用构造函数Box，提供第一个元素的参数
        Box(15,18,20),                          //调用构造函数Box，提供第二个元素的参数
        Box(16,20,26)                           //调用构造函数Box，提供第三个元素的参数
        };

    cout<<"volume of a[0] is "<<a[0].volume()<<endl;         //调用a[0]的volume函数
    cout<<"volume of a[1] is "<<a[1].volume()<<endl;         //调用a[1]的volume函数
    cout<<"volume of a[2] is "<<a[2].volume()<<endl;         //调用a[2]的volume函数
   
   Box b[2]=
    {
        Box(11,11),     call of overloaded `Box(int, int)' is ambiguous   好像是引用模糊，不确定的意思
        Box(12,12)      call of overloaded `Box(int, int)' is ambiguous
       };
    cout<<"square of b[0] is "<<b[0].square()<<endl;
    cout<<"square of b[1] is "<<b[1].square()<<endl;   
    system("PAUSE");
    return EXIT_SUCCESS;
}