How to postpone implementation of abstract class in c++

[C++ Programming]

End Google Ads 201810 - BS.net 01 --> can anybody let me how to postpone implementation of abstract class methods
#include
using namespace std;
class abstrs
{
public:
virtual int add(int i,int j)=0;
virtual int Substract(int i,int j)=0;


};
class derieved : public abstrs
{
public :
virtual int add(int i,int c)
{
return 100;

}//i dont want to implement this piece of code as of now.
/*virtual int Substract(int i,int c)
{
return 100;
}*/
};
int main()
{
derieved dr;
int count=dr.add(12,34);
cout