Only parameterized CTOR: Demo (along with error by g++)

#include <iostream>
using namespace std;

class SI
{
   float pple;
   float rate;
   float n;

   public:
     //
     // We have written only parameterized CTOR
     // In this case, C++ DOES NOT PROVIDE US WITH
     // default constructor.
     //
     SI(float rate, float n)
     {
        this->rate = rate;
        this->n = n;
     }
      void SetInput(float pple);
      void SetInput(float pple, float n, float r);
      float  CalculateSI();
};

void SI::SetInput(float pple)
{
   this->pple = pple;
}
void SI::SetInput(float pple, float n, float rate)
{
    this->pple = pple;
    this->rate = rate;
    this->n = n;
}

float SI::CalculateSI()
{
  return (pple *rate * n) /100;
}

int main()
{
  SI s1;
  s1.SetInput( 1000);
  s1.SetInput(1000, 6.7, 4);
 cout << endl <<"\t Simple intereset = "<< s1.CalculateSI()<< endl;

  return 0;
}
/*
ctor_only_param.cpp:44: error: no matching function for call to ‘SI::SI()’
ctor_only_param.cpp:16: note: candidates are: SI::SI(float, float)
ctor_only_param.cpp:5: note:                 SI::SI(const SI&)
*/